Etymology
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fraction (n.)
late 14c., originally in the mathematical sense, from Anglo-French fraccioun (Old French fraccion, "a breaking," 12c., Modern French fraction) and directly from Late Latin fractionem (nominative fractio) "a breaking," especially into pieces, in Medieval Latin "a fragment, portion," noun of action from past participle stem of Latin frangere "to break (something) in pieces, shatter, fracture," from Proto-Italic *frang-, from a nasalized variant of PIE root *bhreg- "to break." Meaning "a breaking or dividing" in English is from early 15c.; sense of "broken off piece, fragment," is from c. 1600.
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fractional (adj.)
1670s, from fraction + -al (1). Related: Fractionally.
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fractious (adj.)
"apt to quarrel," 1725, from fraction in an obsolete sense of "a brawling, discord" (c. 1500) + -ous; probably on model of captious. Related: Fractiously; fractiousness.
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integer (n.)

"a whole number" (as opposed to a fraction), 1570s, from noun use of Latin integer (adj.) "intact, whole, complete," figuratively, "untainted, upright," literally "untouched," from in- "not" (see in- (1)) + root of tangere "to touch" (from PIE root *tag- "to touch, handle"). The word was used earlier in English as an adjective in the Latin sense, "whole, entire" (c. 1500).

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*bhreg- 

Proto-Indo-European root meaning "to break."

It forms all or part of: anfractuous; Brabant; bracken; brake (n.1) "stopping device for a wheel;" brake (n.2) "kind of fern;" brash; breach; break; breccia; breeches; brioche; chamfer; defray; diffraction; fractal; fraction; fractious; fracture; fragile; fragility; fragment; frail; frangible; infraction; infringe; irrefragable; irrefrangible; naufragous; ossifrage; refract; refraction; refrain (n.); refrangible; sassafras; saxifrage; suffragan; suffrage.

It is the hypothetical source of/evidence for its existence is provided by: Sanskrit (giri)-bhraj "breaking-forth (out of the mountains);" Latin frangere "to break (something) in pieces, shatter, fracture;" Lithuanian braškėti "crash, crack;" Old Irish braigim "break wind;" Gothic brikan, Old English brecan "to break."

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mero- 

before vowels mer-, word-forming element meaning "part, partial, fraction," from Greek meros "a part, a fraction," from PIE root *(s)mer- (2) "to get a share of something."

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split-second (n.)
1884, originally the name of a type of stopwatch with two second hands that could be stopped independently. Meaning "a fraction of a second" is from 1912, from split (adj.) + second (n.1); adjectival meaning "occurring in a fraction of a second" is from 1946.
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decimal (adj.)

c. 1600, "pertaining to a tenth or ten," from Medieval Latin decimalis "of tithes or tenths," from Latin decimus "tenth," from decem "ten" (from PIE root *dekm- "ten"). Applied to Arabic notation before modern use in reference to decimal fractions (fraction whose denominator is a power of 10) emerged 1610s. As a noun from 1640s, "a decimal fraction." Decimal point is by 1711; the use of the point seems to be due to Scottish mathematician John Napier, "Marvellous Merchiston," c. 1619.

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ex parte 

Latin legal term, "on the one side only," from ex "out of" (see ex-) + parte, ablative of pars "a part, piece, a division, a fraction, a side of the body" (from PIE root *pere- (2) "to grant, allot").

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feedback (n.)
1920, in the electronics sense, "the return of a fraction of an output signal to the input of an earlier stage," from verbal phrase, from feed (v.) + back (adv.). Transferred use, "information about the results of a process" is attested by 1955.
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