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 forms

sum·less, adjectivesum·less·ness, nounout·sum, verb (used with object), out·summed, out·sum·ming.

Can be confused

some sum (see usage note at some)

Definition for sum (2 of 4)


surface-to-underwater missile.

Definition for sum (3 of 4)


variant of sub- before m: summon.

Definition for sum (4 of 4)

cogito, ergo sum

[ koh-gi-toh er-goh soo m; English koj-i-toh ur-goh suhm, er-goh ]
/ ˈkoʊ gɪˌtoʊ ˈɛr goʊ ˈsʊm; English ˈkɒdʒ ɪˌtoʊ ˈɜr goʊ ˈsʌm, ˈɛr goʊ /


I think, therefore I am (stated by Descartes as the first principle in resolving universal doubt).
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2019

Examples from the Web for sum

British Dictionary definitions for sum (1 of 3)


/ (sʌm) /


verb sums, summing or summed

(often foll by up) to add or form a total of (something)
(tr) to calculate the sum of (the terms in a sequence)
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

British Dictionary definitions for sum (2 of 3)


/ (sʊm) /

noun plural sumy (sʊmɪ)

the standard monetary unit of Uzbekistan, divided into 100 tiyin

British Dictionary definitions for sum (3 of 3)

cogito, ergo sum

/ Latin (ˈkɒɡɪˌtəʊ ˈɜːɡəʊ ˈsʊm) /

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

Science definitions for sum


[ sŭm ]

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.
The American Heritage® Science Dictionary Copyright © 2011. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.