Dictionary.com
definitions

first

[furst]
See more synonyms for first on Thesaurus.com
adjective
  1. being before all others with respect to time, order, rank, importance, etc., used as the ordinal number of one: the first edition; the first vice president.
  2. Music. highest or chief among several voices or instruments of the same class: first alto; first horn.
  3. Automotive. low1(def 31).
  4. (often initial capital letter) being a member of the household or an intimate acquaintance of the president of the U.S. or of the governor of a state: the First Lady; Checkers, the first dog.
adverb
  1. before all others or anything else in time, order, rank, etc.
  2. before some other thing, event, etc.: If you're going, phone first.
  3. for the first time: She first visited Atlanta in 1980.
  4. in preference to something else; rather; sooner: I'd die first.
  5. in the first place; firstly.
noun
  1. the person or thing that is first in time, order, rank, etc.
  2. the beginning.
  3. the first part; first member of a series.
  4. Music.
    1. the voice or instrument that takes the highest or chief part in its class, especially in an orchestra or chorus.
    2. a leader of a part or group of performers.
  5. Automotive. low gear; first gear: She shifted into first and drove off.
  6. the winning position or rank in a race or other competition.
  7. Baseball. first base.
  8. Usually firsts. Commerce.
    1. a product or goods of the first or highest quality.
    2. goods produced according to specifications, without visible flaws.
    Compare second1(def 23), third(def 12).
  9. British University.
    1. first-class honors.Compare class(def 18).
    2. a person who has won such honors.
Idioms
  1. first and last, everything considered; above all else; altogether: First and last, it is important to know oneself.
  2. first off, Informal. at the outset; immediately: He wanted to know first off why he hadn't been notified.
  3. first thing, before anything else; at once; promptly: I'll call you first thing when I arrive.

Origin of first

before 1000; Middle English; Old English fyr(e)st (see fore1, -est1); cognate with German Fürst prince
Related formsfirst·ness, adjective
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2019

Related Words for first thing

foremost, immediately, firstly, primo
British Dictionary definitions for first thing

first

adjective (usually prenominal)
    1. coming before all others; earliest, best, or foremost
    2. (as noun)I was the first to arrive
  2. preceding all others in numbering or counting order; the ordinal number of one . Often written: 1st
  3. rated, graded, or ranked above all other levels
  4. denoting the lowest forward ratio of a gearbox in a motor vehicle
  5. music
    1. denoting the highest part assigned to one of the voice parts in a chorus or one of the sections of an orchestrafirst soprano; the first violins
    2. denoting the principal player in a specific orchestral sectionhe plays first horn
  6. first thing as the first action of the dayI'll see you first thing tomorrow
  7. first things first things must be done in order of priority
  8. the first thing (in negative constructions) even one thinghe doesn't know the first thing about me
noun
  1. the beginning; outsetI knew you were a rogue from the first; I couldn't see at first because of the mist
  2. education, mainly British an honours degree of the highest classFull term: first-class honours degree
  3. something which has not occurred beforea first for the company
  4. the lowest forward ratio of a gearbox in a motor vehicle; low gear
  5. music
    1. the highest part in a particular section of a chorus or orchestra
    2. the instrument or voice taking such a part
    3. the chief or leading player in a section of an orchestra; principal
  6. music a rare word for prime (def. 11)
adverb
  1. before anything else in order, time, preference, importance, etcdo this first; first, remove the head and tail of the fish
  2. first and last on the whole; overall
  3. from first to last throughout
  4. for the first timeI've loved you since I first saw you
  5. (sentence modifier) in the first place or beginning of a series of actionsfirst I want to talk about criminality
See also firsts

Word Origin for first

Old English fyrest; related to Old Saxon furist, Old Norse fyrstr, German Fürst prince, one who is first in rank
Collins English Dictionary - Complete & Unabridged 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012
Word Origin and History for first thing

first

adj., adv.

Old English fyrst "foremost," superlative of fore; from Proto-Germanic *furisto- (cf. Old Saxon fuirst "first," Old High German furist, Old Norse fyrstr, Danish første, Old Frisian ferist, Middle Dutch vorste "prince," Dutch vorst "first," German Fürst "prince"), superlative of *fur-/*for-, from PIE root *per- (1) "forward, through" (see per).

First-class (adj.) is from 1837; first-rate (1660s) is from classes of warships in the British navy. First aid is that given at the scene, pending the arrival of a doctor.

First Lady as an informal title for the wife of a U.S. president was in use by 1908, short for First lady of the land (by 1863 with reference to the president's wife). First name is attested from mid-13c.; first-born is from mid-14c. First base "a start" (1938) is a figurative use from the game of baseball.

Online Etymology Dictionary, © 2010 Douglas Harper
first thing in Medicine

first

[fûrst]
adj.
  1. Coming before all others in order or location.
  2. Occurring or acting before all others in time; earliest.
  3. Being the innermost digit, especially on a foot.
Related formsfirst n.
The American Heritage® Stedman's Medical Dictionary Copyright © 2002, 2001, 1995 by Houghton Mifflin Company. Published by Houghton Mifflin Company.
Idioms and Phrases with first thing

first thing

Before anything else; without delay. For example, Tom was supposed to call him first thing in the morning. [Late 1500s] Also see under first and foremost; first off.

first

In addition to the idioms beginning with first

  • first and foremost
  • first and last
  • first blush
  • first come, first served
  • first cousin
  • first hand
  • first of all
  • first off
  • first thing
  • first things first

also see:

  • at first
  • at first blush
  • at first hand
  • cast the first stone
  • get to first base
  • if at first you don't succeed
  • in the first place
  • in the (first) flush of
  • love at first sight
  • not know beans (the first thing)
  • of the first water
  • on a first-name basis
The American Heritage® Idioms Dictionary Copyright © 2002, 2001, 1995 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company.