Etymology
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function (n.)

1530s, "one's proper work or purpose; power of acting in a specific proper way," from French fonction (16c.) and directly from Latin functionem (nominative functio) "a performance, an execution," noun of action from funct-, past-participle stem of fungi "perform, execute, discharge," from PIE *bhung- "be of use, be used" (source also of Sanskrit bhunjate "to benefit, make benefit, atone," Armenian bowcanem "to feed," Old Irish bongaid "to break, harvest"), which is perhaps related to root *bhrug- "to enjoy." Meaning "official ceremony" is from 1630s, originally in church use. Use in mathematics probably was begun by Leibnitz (1692). In reference to computer operations, 1947.

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manifest (n.)

"certified list of a ship's cargo," for use by Customs, 1706; see manifest (adj.). Earlier, "a public declaration" (1610s; compare manifesto), from French manifeste, verbal noun from manifester. Earlier still in English as "a manifestation" (1560s).

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function (v.)

1844, "perform a function" (intransitive), from function (n.). Related: Functioned; functioning.

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manifest (adj.)
Origin and meaning of manifest

late 14c., "clearly revealed to the eye or the understanding, open to view or comprehension," from Old French manifest "evident, palpable," (12c.), or directly from Latin manifestus "plainly apprehensible, clear, apparent, evident;" of offenses, "proved by direct evidence;" of offenders, "caught in the act," probably from manus "hand" (from PIE root *man- (2) "hand") + -festus, which apparently is identical to the second element of infest.

De Vaan writes, "If manifestus may be interpreted as 'caught by hand', the meanings seem to point to 'grabbing' or 'attacking' for -festus." But he finds none of the proposed ulterior connections compelling, and concludes that, regarding infestus and manifestus, "maybe the two must be separated." If not, the sense development might be from "caught by hand" to "in hand, palpable." 

Manifest destiny, "that which clearly appears destined to come to pass; a future state, condition, or event which can be foreseen with certainty, or is regarded as inevitable" was much used in American politics from about the time of the Mexican War "by those who believed that the United States were destined in time to occupy the entire continent" [Century Dictionary].

Other nations have tried to check ... the fulfillment of our manifest destiny to overspread the Continent allotted by Providence for the free development of our yearly multiplying millions. [John O'Sullivan (1813-1895), "U.S. Magazine & Democratic Review," July 1845]

The phrase apparently is O'Sullivan's coinage; the notion is as old as the republic.

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manifest (v.)
Origin and meaning of manifest

late 14c., "to spread" (one's fame), "to show plainly," from manifest (adj.) or else from Latin manifestare "to discover, disclose, betray." Meaning "to display by actions" is from 1560s; reflexive sense, of diseases, etc., "to reveal as in operation" is from 1808. Related: Manifested; manifesting.

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dysfunction (n.)

"failure to function, abnormality or impairment of function," 1914, from dys- "bad, abnormal, difficult" + function (n.). Originally in anatomy and medicine; in sociology by 1949.

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phanero- 

before vowels phaner-, word-forming element meaning "visible, manifest," especially from 18c. in biology, from Greek phaneros "visible, manifest, evident, apparent," from phainein "bring to light, cause to appear, show," from PIE root *bha- (1) "to shine." Opposed to crypto-.

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manifestly (adv.)

"clearly, unmistakably, evidently," early 15c., from manifest (adj.) + -ly (2).

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malfunction (n.)

"a faulty functioning, a failure to function as expected," 1827, from mal- "bad, badly, wrong" + function. As a verb, "to fail to function normally or as expected," by 1888. Related: Malfunctioned; malfunctioning.

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