-
a
aindefinite articlenot any particular or certain one of a class or group.
-
A
Anounthe first letter of the English alphabet, a vowel.
-
Å
Åangstrom.
-
a'
a'adjectiveall.
-
a-
a-a reduced form of the Old English preposition on, meaning “on,” “in,” “into,” “to,” “toward,” preserved before a noun in a prepositional phrase, forming a predicate adjective or an adverbial element (afoot; abed; ashore; aside; away ), or before an adjective (afar; aloud; alow ), as a moribund prefix with a verb (acknowledge ), and in archaic and dialectal use before a present participle in -ing (set the bells aringing ); and added to a verb stem with the force of a present participle (ablaze; agape; aglow; astride; and originally,awry ).
-
-a
-aa plural ending of nouns borrowed from Greek and Latin.
-
A-
A-atomic (used in combination).
-
a.
a.abbreviationyear.
-
A.
A.abbreviationyear.
-
a–
a–A prefix meaning “without” or “not” when forming an adjective (such as amorphous, without form, or atypical, not typical), and “absence of” when forming a noun (such as arrhythmia, absence of rhythm). Before a vowel or h it becomes an– (as in anhydrous, anoxia).
a
1 Americanindefinite article
-
not any particular or certain one of a class or group.
a man; a chemical; a house.
-
a certain; a particular.
one at a time; two of a kind; A Miss Johnson called.
-
another; one typically resembling.
a Cicero in eloquence; a Jonah.
-
one (used before plural nouns that are preceded by a quantifier singular in form): a hundred men (comparehundreds of men ); a dozen times (comparedozens of times ).
-
indefinitely or nonspecifically (used with adjectives expressing number).
a great many years; a few stars.
-
one (used before a noun expressing quantity).
a yard of ribbon; a score of times.
-
any; a single.
not a one.
preposition
preposition
auxiliary verb
abbreviation
noun
-
A's,
plural
-
As,
plural
-
a's,
plural
-
as
plural
-
the first letter of the English alphabet, a vowel.
-
any spoken sound represented by the letter A or a, as in bake, hat, father, or small.
-
something having the shape of an A .
-
a written or printed representation of the letter A or a.
-
a device, as a printer's type, for reproducing the letter A or a.
idioms
-
not know from A to B, to know nothing; be ignorant.
-
from A to Z, from beginning to end; thoroughly; completely.
He knows the Bible from A to Z.
-
the first in order or in a series.
-
Sometimes a
-
(in some grading systems) a grade or mark, as in school or college, indicating the quality of a student's work as excellent or superior.
-
(in some school systems) a symbol designating the first semester of a school year.
-
-
Music.
-
the sixth tone in the scale of C major or the first tone in the relative minor scale, A minor.
-
a string, key, or pipe tuned to this tone.
-
a written or printed note representing this tone.
-
(in the fixed system of solmization) the sixth tone of the scale of C major, called la.
-
the tonality having A as the tonic note.
-
-
Physiology. a major blood group, usually enabling a person whose blood is of this type to donate blood to persons of group A or AB and to receive blood from persons of O or A.
-
Sometimes a the medieval Roman numeral for 50 or 500.
-
Chemistry. (formerly) argon.
-
Chemistry, Physics. mass number.
-
Biochemistry.
-
Logic. Also a universal affirmative.
-
British. a designation for a motion picture recommended as suitable for adults.
-
a proportional shoe width size, narrower than B and wider than AA.
-
a proportional brassiere cup size, smaller than B and larger than AA.
-
a quality rating for a corporate or municipal bond, lower than AA and higher than BBB.
adjective
abbreviation
abbreviation
abbreviation
-
about.
-
acre; acres.
-
active.
-
adjective.
-
alto.
-
ampere; amperes.
-
anonymous.
-
answer.
-
are; ares.
-
Baseball. assist; assists.
abbreviation
abbreviation
abbreviation
-
Absolute.
-
Academy.
-
acre; acres.
-
America.
-
American.
-
angstrom.
-
answer.
-
April.
-
Artillery.
symbol
-
music
-
a note having a frequency of 440 hertz ( A above middle C ) or this value multiplied or divided by any power of 2; the sixth note of the scale of C major
-
a key, string, or pipe producing this note
-
the major or minor key having this note as its tonic
-
-
a human blood type of the ABO group, containing the A antigen
-
(in Britain) a major arterial road
the A3 runs from London to Portsmouth
-
-
a film certified for viewing by anyone, but which contains material that some parents may not wish their children to see
-
( as modifier )
an A film
-
-
mass number
-
the number 10 in hexadecimal notation
-
cards ace
-
chem argon (now superseded by Ar )
-
ampere(s)
-
Also: at. ampere-turn
-
absolute (temperature)
-
(in circuit diagrams) ammeter
-
area
-
(in combination) atomic
an A-bomb
an A-plant
-
chem affinity
-
biochem adenine
-
logic a universal affirmative categorical proposition, such as all men are mortal: often symbolized as SaP Compare E I 2 O 1
-
-
a person whose job is in top management, or who holds a senior administrative or professional position
-
( as modifier ) See also occupation groupings
an A worker
-
abbreviation
determiner
-
used preceding a singular countable noun, if the noun is not previously specified or known
a dog
a terrible disappointment
-
used preceding a proper noun to indicate that a person or thing has some of the qualities of the one named
a Romeo
a Shylock
-
used preceding a noun or determiner of quantity
a cupful
a dozen eggs
a great many
to read a lot
-
used preceding a noun indicating a concrete or abstract thing capable of being divided
half a loaf
a quarter of a minute
-
each or every; per
once a day
fifty pence a pound
-
a certain; one
to change policy at a stroke
a Mr Jones called
-
(preceded by not) any at all
not a hope
symbol
-
acceleration
-
are(s) (metric measure of land)
-
atto-
-
chess See algebraic notation
noun
-
the first letter and first vowel of the modern English alphabet
-
any of several speech sounds represented by this letter, in English as in take, bag, calm, shortage, or cobra
-
Also called: alpha. the first in a series, esp the highest grade or mark, as in an examination
-
from start to finish, thoroughly and in detail
abbreviation
-
acre(s) or acreage
-
America(n)
-
answer
prefix
-
on; in; towards
afoot
abed
aground
aback
-
literary (used before a present participle) in the act or process of
come a-running
go a-hunting
-
in the condition or state of
afloat
alive
asleep
symbol
prefix
verb
preposition
determiner
Grammar
In both spoken and written English the choice of a1 or an 1 is determined by the initial sound of the word that follows. Before a consonant sound, a is used; before a vowel sound, an : a book, a rose; an apple, an opera. Problems arise occasionally when the following word begins with a vowel letter but actually starts with a consonant sound, or vice versa. Some words beginning with the vowel letter u and all words beginning with the vowel letters eu are pronounced with a beginning consonant sound, as if the first letter were y : a union; a European. Some other spellings that begin with a vowel letter may also stand for an initial consonant sound: a ewe; a ewer. The words one and once and all compounds of which they are the first element begin with a w sound: a one-room apartment; a once-famous actor. The names of the consonant letters f, h, l, m, n, r, s, and x are pronounced with a beginning vowel sound. When these letters are used as words or to form words, they are preceded by an : to rent an L-shaped studio; to fly an SST. The names of the vowel letter u and the semivowel letters w and y are pronounced with a beginning consonant sound. When used as words, they are preceded by a : a U-turn; The plumber installed a Y in the line. In some words beginning with the letter h, the h is not pronounced; the words actually begin with a vowel sound: an hour; an honor. When the h is strongly pronounced, as in a stressed syllable at the beginning of a word, it is preceded by a : a history of the Sioux; a hero sandwich. (In former times an was used before strongly pronounced h in a stressed first syllable: an hundred. ) Such adjectives as historic, historical, heroic, and habitual, which begin with an unstressed syllable and often with a silent or weakly pronounced h, are commonly preceded by an, especially in British English. But the use of a rather than an is widespread in both speech and writing: a historical novel; a habitual criminal. Hotel and unique are occasionally preceded by an, but this use is increasingly old-fashioned. Although in some dialects an has yielded to a in all cases, edited writing reflects usage as described above.
Other Word Forms
Noun Inflected Forms
Etymology
Origin of a1
First recorded in 1200–50; Middle English; originally preconsonantal phonetic variant of an 1
Origin of a2
Originally Middle English a, preconsonantal variant of on ( a- 1 ); confused with a 1
Origin of a3
Middle English; unstressed preconsonantal variant of of 1
Origin of a4
First recorded in 1300–50; Middle English; a phonetic variant of have
Origin of a5
First recorded in 1200–50; Middle English a, ha
Origin of a-12
Middle English, late Old English; cf. a 2, nowadays
Origin of a-13
Middle English; see a 3
Origin of a-14
Middle English; Old English a- (unstressed), ǣ-, ā-, ō- (stressed; see abb, woof 1, oakum), rarely or- ( see ordeal), ultimately from unattested Germanic uz- from unstressed Indo-European uss-, from ud-s (these latter two also unattested), akin to out; in some cases confused with a- 4, as in abridge
Origin of a-15
Middle English < Latin ā-, a- (variant of ab- ab- ); in some words < French a- < Latin ab-, as in abridge
Origin of a-16
Middle English, in some words < Middle French a- < Latin ad- prefix or ad preposition ( ad- ), as in abut; in others < Latin a- (variant of ad- ad- ), as in ascend
Origin of -a20
From Latin feminine ending -a, as Claudia, feminine of Claudius; see -a 2
Origin of -a21
Probably generalized from the -a of magnesia
Origin of a.23
< Latin annō, ablative of annus
Origin of a.24
From the Latin word ante
Origin of A.26
< Latin annō, ablative of annus
Origin of A.27
From the Latin word ante
Example Sentences
Examples are provided to illustrate real-world usage of words in context. Any opinions expressed do not reflect the views of Dictionary.com.
See Examples For:
In benchmarking of models’ cyber strengths, AIs are told to gain access to a computer system.
From The Wall Street Journal ● Aug. 5, 2026
Anthropic’s Mythos, they discovered, was in the midst of what is known as a supply chain attack.
From The Wall Street Journal ● Aug. 5, 2026
Its goal was to succeed at a benchmarking test, the security research agency said.
From The Wall Street Journal ● Aug. 5, 2026
Testers at the AI Security Institute didn’t expect the Anthropic and OpenAI models to go rogue but realized that something had gone awry when they received a strange alert the morning of July 28.
From The Wall Street Journal ● Aug. 5, 2026
She has retired from her most recent job as a bank secretary and has dedicated much of her time as a volunteer usher at the Kennedy Center for the Performing Arts in Washington, DC.
From "At Last She Stood" by Erin Entrada Kelly
![]()
A U.K. government-backed AI research institute said Tuesday that during routine tests, models built by OpenAI and Anthropic unexpectedly took “autonomous, unsanctioned action on the live internet, targeting real people and organisations.”
From The Wall Street Journal ● Aug. 5, 2026
A key part of this year's Han Kuang exercise is decentralising command and control to enable commanders and officers on the battlefield to make operational decisions without waiting for orders.
From Barron's ● Aug. 5, 2026
A man who was reported missing in Fawnskin on Monday morning was found deceased by the San Bernardino Sheriff’s Department near his campsite after an extensive search.
From Los Angeles Times ● Aug. 5, 2026
A spokesperson for Storonsky's family office told the paper the claim was "without merit and will be defended".
From BBC ● Aug. 5, 2026
A line is drawn between their center point to lay out a hypothetical path for the tamping iron.
From "Phineas Gage" by John Fleischman
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In the new study, the research team employed state-of-the-art cryo-electron microscopy techniques to capture nine different states associated with the lipid transport and determine structures at 2.4 to 3.1 Å resolution for these states.
From Science Daily ● Dec. 5, 2023
Danish, an often staccato language spoken by only about six million people and whose alphabet includes the letters Æ, Ø and Å, is perhaps an unlikely choice for pop’s next lingua franca.
From New York Times ● Apr. 19, 2023
Note: The length unit angstrom, Å, is often used to represent atomic-scale dimensions and is equivalent to 10−10 m.
From Textbooks ● Feb. 14, 2019
At the first epoch, all deviations from the blackbody spectrum are below about 10% in the range 3,500 Å–20,000 Å, indicating that the fit is very satisfactory.
From Nature ● Oct. 15, 2017
Observations were made with the spectrograph configuration, using a grating with 600 lines per millimetre, which gave a resolution of 2.3 Å per pixel covering 3,700–7,700Å.
From Nature ● Apr. 4, 2014
Its name comes from the Scottish Gaelic word cheò, meaning mist, and is a reference to the Gaelic name of Isle of Syke - Eilean a' Cheò or Isle of Mist.
From BBC ● Feb. 5, 2024
Some songs—such as “A Guid New Year to ane a’ A’”—were widely recognized.
From National Geographic ● Dec. 27, 2023
Whether all this adds up to some big change a’ coming to City Hall, it’s too soon to say.
From Seattle Times ● May 24, 2023
Continue round into Glen Pean and up to the Bealach a’ Chaorainn.
From The Guardian ● Feb. 29, 2020
“No, you. I forget some a’ the things.
From "Of Mice and Men" by John Steinbeck
![]()
And, uh, you know, it's just a- a very bad situation.
From Scientific American ● May 4, 2023
That giant thing of spices that looks like a-
From Salon ● Mar. 30, 2019
Average sizes are about 2.0 μm and 1.2 μm along the a- and c-axes, respectively. b, AFM height image and height profiles for the MFI nanosheets.
From Nature ● Mar. 14, 2017
The Israeli grandmaster plays the positional side of a Benko Gambit to perfection, building up great pressure on the a- and b-files while the great Benko bishop strafes the White position from g7.
From Washington Times ● May 12, 2015
You wouldn’t ha’ believed in them first days of April that trouble was a- brewin’ fer all of us—ever’ one was feelin’ good, and we was gettin’ along so fine.”
From "Across Five Aprils" by Irene Hunt
![]()
Usually words ending in "-o" are masculine and those ending in "-a" are feminine, but there are many common words that break those gender rules, like "la mano," the word for "hand."
From Salon ● Sep. 26, 2022
Primarily, of course, the events are a hugely important commemoration of the Queen's death -a global tribute to the woman who was one of the most recognisable world leaders for so long.
From BBC ● Sep. 17, 2022
Winston, the No. 1 overall pick from the 2015 draft, has one turnover in the past three games, -a meaningless interception with 1 second remaining in last week’s 28-14 loss to the Saints.
From Washington Times ● Dec. 13, 2018
He needs to grow up or get out -a cancer in the locker room.
From New York Times ● Jan. 9, 2017
‘I’m not -a thief!’ coughed Torak, snatching at his throat.
From "Wolf Brother" by Michelle Paver
![]()
"The All Blacks are a classy outfit, and they'll punish you if you're not on your A- game, and at times we weren't," admitted Irish skipper Dan Sheehan.
From BBC ● Jul. 18, 2026
Yet the average high-school math GPA was an A- for students taking a middle-school remedial course.
From The Wall Street Journal ● Nov. 24, 2025
The difference between an A- and an A+, according to the report, could depend on how much spring precipitation the region receives.
From Los Angeles Times ● May 12, 2024
Normally it’s sort of fun to count the A- , B-, and Z-listers shilling for mayonnaise and sneakers.
From Slate ● Feb. 12, 2024
In 1926 it was decided to build A- and B-blocks on the hill, and in 1929 they were completed, along with the chapel and mess hall.
From "Newjack: Guarding Sing Sing" by Ted Conover
![]()
Use your answers to parts a. and d. to determine which of the three options is best.
From Textbooks ● Mar. 30, 2016
You may notice that the graphs in parts a. and b. are identical.
From Textbooks ● Mar. 30, 2016
Rewrite the integral in part a. as an equivalent integral in five other orders.
From Textbooks ● Mar. 30, 2016
Use a. to find the rate at which the volume is changing at t = 1 min.
From Textbooks ● Mar. 30, 2016
“I wish I could live somewhere where there were books all around. In a real town, with a. real library. And I could read about pirates or explorers or anything.”
From "Hattie Big Sky" by Kirby Larson
![]()
"This is a colossal opening," said analyst David A. Gross of Franchise Entertainment Research.
From Barron's ● Aug. 2, 2026
“Versions of this case have played out in federal courts across the country,” Judge Daniel A. Bress wrote for the 9th Circuit on Thursday.
From Los Angeles Times ● Jul. 31, 2026
It is Exhibit A. A guarantee that demands this much luck, money, and endurance before a court will enforce it has not been functioning as a guarantee.
From Slate ● Jul. 28, 2026
The film from Universal had an "outstanding hold" for its second weekend, industry analyst David A. Gross said, after it dropped only about 30 percent from its $124 million debut.
From Barron's ● Jul. 26, 2026
Nevertheless, he wanted Madison to know that it came at a price: “Mr. A. and myself were cordial friends from the beginning of the revolution,” he explained.
From "Founding Brothers: The Revolutionary Generation" by Joseph J. Ellis
![]()
You know, that’s actually the easiest of all things, if you look, cause it’s such a–
From Slate ● Jan. 22, 2020
The montage ends with a honest rap from Issa: “I don’t want to be here, but my ex won’t take me back. So my broken a– is here, small-talking over apps.”
From Washington Post ● Jul. 28, 2017
We created a– civilian review board, gave them their own detectives.
From Time ● Jan. 17, 2016
MELBER: Now your path here– involved time as a– as a lawyer and a prosecutor.
From MSNBC ● Feb. 12, 2015
But whatever happens, you’ll 240 believe I’ve done my best, won’t you?–even if I’m not a– Promise me straight, you’ll lock up tight every night.”
From Into the Primitive by Bennett, Robert Ames
Palestra spent last season on loan at Cagliari and was named Serie A's defender of the year.
From BBC ● Jul. 1, 2026
Seriously, the dude’s shrieks could be heard echoing in the A’s dugout on the NBC Sports California broadcast of the game.
From Los Angeles Times ● Jul. 1, 2026
The A’s scored the final run on a wild pitch in the ninth.
From Los Angeles Times ● Jun. 30, 2026
In the same way a dismal class performance on a business school exam will still yield some A’s, curves also apply in the stock market when a company’s results aren’t necessarily jumping off the page.
From Barron's ● Jun. 29, 2026
“Did you know, Amir jan, that she earned nothing but A’s in high school?”
From "The Kite Runner" by Khaled Hosseini
![]()
"As the population moves toward 10 billion, energy issues will become just as critical as food issues," said Nakagawa, chief executive of design firm Tripod Design.
From Barron's ● Aug. 5, 2026
As it stands, Mattel remains firmly stuck in the toy aisle, with the majority of its revenue coming from toy sales.
From The Wall Street Journal ● Aug. 4, 2026
As she explained her rationale, Halem, who appeared in court in an orange jumpsuit, sat with his head bowed, eyes downcast.
From Los Angeles Times ● Aug. 4, 2026
As José Carlos Cueto reports, while the bill was passed unanimously in Colombia's Congress, it follows a long battle to eradicate the dangerous and often secretive procedure.
From BBC ● Aug. 4, 2026
“That is a part of life, shiyáázh. As much as we want, we can’t change it. We also can’t ignore it.”
From "Legendary Frybread Drive-In" by Cynthia Leitich Smith
![]()
Like other Romance languages, Spanish divides most endings of nouns into masculine o’s or feminine a’s.
From Washington Times ● Dec. 12, 2021
And then, every fourth January, we’re suddenly expected to say it, to spell it, to know where to place the u’s and a’s.
From New York Times ● Jan. 19, 2017
The U.A.W. also objects to Hon a's habit of calling its employees "associates," complaining that this is intended to blur labor-management distinctions in the workers' minds.
From Time Magazine Archive
![]()
It kept reading my a's as g's or u's, my b's as d's and sprinkling periods liberally throughout my text.
From Time Magazine Archive
![]()
“Because, see, we’re in Spanish class with all the a's and o’s at the end, and Troy just comes up with this name, Ema, just like that, and boom, it stuck. You see?”
From "Shelter (Book One): A Mickey Bolitar Novel" by Harlan Coben
![]()
The industry as a whole isn’t applying enough rigor to what have become dangerous experiments, said Joshua Saxe, the chief technology officer with the AI security company Abundant Security.
From The Wall Street Journal ● Aug. 5, 2026
They jeered even louder and longer as he took the mound in the bottom of the first inning.
From Los Angeles Times ● Aug. 5, 2026
He has described his past views as "indefensible" and now speaks out against extremism.
From BBC ● Aug. 5, 2026
Anthropic’s Mythos, they discovered, was in the midst of what is known as a supply chain attack.
From The Wall Street Journal ● Aug. 5, 2026
Finally, she reaches the American camp, where she is brought to a man known only as “Captain Blair.”
From "At Last She Stood" by Erin Entrada Kelly
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Definitions and idiom definitions from Dictionary.com Unabridged, based on the Random House Unabridged Dictionary, © Random House, Inc. 2023
Idioms from The American Heritage® Idioms Dictionary copyright © 2002, 2001, 1995 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company.