-sum-

WordReference Random House Learner's Dictionary of American English © 2025

sum /sʌm/   n., v., summed, sum•ming. 
n. [countable]

1. Mathematics the total of two or more numbers, amounts, or quantities, determined by or as if by addition:
   The sum of 6 and 8 is 14.
2. an amount or quantity, esp. of money:
   to lend small sums.
3. Mathematics a series of numbers or quantities to be added up.
4. the full amount, or the whole:
   the sum of our knowledge.
5. the main idea, gist, or point:
   the sum and substance of his argument.

v. 

6. Mathematics [~ + object] to figure out the sum of, as by addition.
7. sum up:
   • to express in a brief yet complete statement;
     summarize: [~ + up + object]
     He summed up the main points of the speech.
     [~ + object + up]
     Can you sum it all up in just a few words?
     [no object]
     ready to sum up at last after a long speech.
   • to form a quick estimate or judgment of: [~ + up + object]
     quickly summed up the situation.
     [~ + object + up]
     She summed him up in a minute.

Idioms

8. Idioms in sum, in brief but complete form:
   In sum, the government believes it knows what it is doing.

-sum-, root. 

1. -sum- comes from Latin, where it has the meaning "take up;
   pick up.'' This meaning is found in such words as: assume, consume, consumption, presume, presumption, resume, resumé, resumption, subsume.

WordReference Random House Unabridged Dictionary of American English © 2025

sum (sum),  n., v., summed, sum•ming. 

n. 

1. Mathematics 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, esp. with reference to money:
   The expenses came to an enormous sum.
3. an indefinite amount or quantity, esp. of money:
   to lend small sums.
4. Mathematics a series of numbers or quantities to be added up.
5. Mathematics 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
   • the limit of the sequence of partial sums of a given infinite series.
   • union (def. 10a).
10. a summary.

v.t. 

11. to combine into an aggregate or total (often fol. by up).
12. Mathematics to ascertain the sum of, as by addition.
13. to bring into or contain in a small compass (often fol. by up).

v.i. 

14. to amount (usually fol. by to or into):
    Their expenses summed into the thousands.
15. sum up:
    • to reckon:
      We summed up our assets and liabilities.
    • to bring into or contain in a brief and comprehensive statement;
      summarize:
      to sum up the case for the prosecution.
    • to form a quick estimate of:
      I summed him up in a minute.

• Medieval Latin summāre, derivative of summa
• Old French summer)
• Latin summa sum, noun, nominal use of feminine of summus highest, superlative of superus (see superior); (verb, verbal) Middle English summen (
• (noun, nominal) Middle English summe 1250–1300

sum′less, adj. 
sum′less•ness, n. 
Synonyms

• 1. See number. 

sum-, 

1. var. of sub- before
   m: summon.

SUM, 

1. Military surface-to-underwater missile.