Etymology
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sum (n.)
c. 1300, summe, "quantity or amount of money," from Anglo-French and Old French summe, somme "amount, total; collection; essential point; summing up, conclusion" (13c., Modern French somme), from Latin summa "the top, summit; chief place, highest rank; main thing, chief point, essence, gist; an amount (of money)," noun use (via phrases such as summa pars, summa res) of fem. of summus "highest, uppermost," from PIE *sup-mos-, suffixed form of root *uper "over."

The sense development from "highest" to "total number, the whole" probably is 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 now (compare the bottom line).

General sense of "numerical quantity" of anything, "a total number" is from late 14c. Meaning "essence of a writing or speech" also is attested from mid-14c. Meaning "aggregate of two or more numbers" is from early 15c.; sense of "arithmetical problem to be solved" is from 1803. Sum-total is attested from late 14c., from Medieval Latin summa totalis.
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sum (v.)
early 14c., "to count, count up, calculate, reckon," from Old French sommer "to count, add up," or directly from Medieval Latin summare, from summa (see sum (n.)). Meaning "briefly state the substance of" is first recorded 1620s (since c. 1700 usually with up). Related: Summed; summing.
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sum- 
assimilated form of sub- before -m-.
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summary (n.)
"a summary statement or account," c. 1500, from Latin summarium "an epitome, abstract, summary," from summa "totality, gist" (see sum (n.)).
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summary (adj.)
early 15c., "brief, abbreviated; containing the sum or substance only," from Medieval Latin summarius "of or pertaining to the sum or substance," from Latin summa "whole, totality, gist" (see sum (n.)). Compare Latin phrase ad summam "on the whole, generally, in short." Sense of "done promptly, performed without hesitation or formality" is from 1713.
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summation (n.)
1760, "process of calculating a sum," from Modern Latin summationem (nominative summatio) "an adding up," noun of action from Late Latin summatus, past participle of summare "to sum up," from Latin summa (see sum (n.)). Meaning "a summing up" is from 1836.
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dim sum (n.)

"Chinese cuisine prepared as bite-sized portions served in small steamer baskets or on small plates," 1948, from Cantonese tim sam (Chinese dianxin) "appetizer," said to mean literally "touch the heart." Ayto ("Diner's Dictionary") gives the elements as tim "dot" + sam "heart."

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consummate (adj.)

c. 1500, "complete, perfect, carried to the utmost extent or degree," from Latin consummatus "perfected, complete," past participle of consummare "sum up, complete," from assimilated form of com "together, with" (see con-) + summa "sum, total," from summus "highest" (see sum (n.)). Of persons, "accomplished, very qualified," from 1640s. Related: Consummately.

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consummation (n.)

Middle English consummacioun, late 14c., "perfection;" c. 1400, "completion, accomplishment," from Latin consummationem (nominative consummatio) "a summing up; a finishing, a completing," noun of action from past-participle stem of consummare "to sum up, finish," from assimilated form of com "together, with" (see con-) + summa "sum, total," from summus "highest" (see sum (n.)). Sense of "completion of a marriage (by sexual intercourse)" is c. 1530.

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consummate (v.)

mid-15c., "to bring to completion, finish by completing what was intended," from Latin consummatus, past participle of consummare "to sum up, make up, complete, finish," from assimilated form of com "together, with" (see con-) + summa "sum, total," from summus "highest" (see sum (n.)).

Meaning "to bring a marriage to completion" (by sexual intercourse) is from 1530s. Related: Consummated; consummating.

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