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  1. the aggregate of two or more numbers, magnitudes, quantities, or particulars as determined by or as if by the mathematical process of addition: The sum of 6 and 8 is 14.
  2. a particular aggregate or total, especially with reference to money: The expenses came to an enormous sum.
  3. an indefinite amount or quantity, especially of money: to lend small sums.
  4. a series of numbers or quantities to be added up.
  5. an arithmetical problem to be solved, or such a problem worked out and having the various steps shown.
  6. the full amount, or the whole.
  7. the substance or gist of a matter, comprehensively or broadly viewed or expressed: the sum of his opinions.
  8. concise or brief form: in sum.
  9. Mathematics.
    1. the limit of the sequence of partial sums of a given infinite series.
    2. union(def 10a).
  10. a summary.
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verb (used with object), summed, sum·ming.
  1. to combine into an aggregate or total (often followed by up).
  2. to ascertain the sum of, as by addition.
  3. to bring into or contain in a small compass (often followed by up).
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verb (used without object), summed, sum·ming.
  1. to amount (usually followed by to or into): Their expenses summed into the thousands.
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Verb Phrases
  1. sum up,
    1. to reckon: We summed up our assets and liabilities.
    2. to bring into or contain in a brief and comprehensive statement; summarize: to sum up the case for the prosecution.
    3. to form a quick estimate of: I summed him up in a minute.
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Origin of sum

1250–1300; (noun) Middle English summe < Latin summa sum, noun use of feminine of summus highest, superlative of superus (see superior); (v.) Middle English summen (< Old French summer) < Medieval Latin summāre, derivative of summa
Related formssum·less, adjectivesum·less·ness, nounout·sum, verb (used with object), out·summed, out·sum·ming.
Can be confusedsome sum (see usage note at some)

Synonyms for sum

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1. See number.


  1. surface-to-underwater missile.
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  1. variant of sub- before m: summon.
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cogito, ergo sum

[koh-gi-toh er-goh soo m; English koj-i-toh ur-goh suhm, er-goh]
  1. I think, therefore I am (stated by Descartes as the first principle in resolving universal doubt).
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Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2018

Related Words for sum

bulk, amount, worth, value, quantity, body, gross, works, tally, integral, system, entity, aggregate, synopsis, score, mass, totality, summation, epitome, reckoning

Examples from the Web for sum

Contemporary Examples of sum

Historical Examples of sum

British Dictionary definitions for sum


    1. the result of the addition of numbers, quantities, objects, etc
    2. the cardinality of the union of disjoint sets whose cardinalities are the given numbers
  1. one or more columns or rows of numbers to be added, subtracted, multiplied, or divided
  2. maths the limit of a series of sums of the first n terms of a converging infinite series as n tends to infinity
  3. (plural) another name for number work
  4. a quantity, esp of moneyhe borrows enormous sums
  5. the essence or gist of a matter (esp in the phrases in sum, in sum and substance)
  6. a less common word for summary
  7. archaic the summit or maximum
  8. (modifier) complete or final (esp in the phrase sum total)
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verb sums, summing or summed
  1. (often foll by up) to add or form a total of (something)
  2. (tr) to calculate the sum of (the terms in a sequence)
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See also sum up

Word Origin for sum

C13 summe, from Old French, from Latin summa the top, sum, from summus highest, from superus in a higher position; see super


noun plural sumy (sʊmɪ)
  1. the standard monetary unit of Uzbekistan, divided into 100 tiyin
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cogito, ergo sum

  1. I think, therefore I am; the basis of Descartes' philosophy
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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 sum


late 13c., "quantity or amount of money," from Anglo-French and Old French summe (13c.), from Latin summa "total number, whole, essence, gist," noun use of fem. of summus "highest," from PIE *sup-mos-, from root *uper "over" (see super-).

The sense development from "highest" to "total number" is probably via the Roman custom of adding up a stack of figures from the bottom and writing the sum at the top, rather than at the bottom as we do now (cf. the bottom line). Meaning "total number of anything" is recorded from late 14c. Meaning "essence of a writing or speech" also is attested from late 14c. The verb is attested from c.1300; meaning "briefly state the substance of" (now usually with up) is first recorded 1620s. Sum-total is attested from late 14c., from Medieval Latin summa totalis.

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Online Etymology Dictionary, © 2010 Douglas Harper

sum in Science


  1. The result of adding numbers or quantities. The sum of 6 and 9, for example, is 15, and the sum of 4x and 5x is 9x.
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The American Heritage® Science Dictionary Copyright © 2011. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.