Etymology
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aperture (n.)

early 15c., "an opening, hole, orifice," from Latin apertura "an opening," from apertus, past participle of aperire "to open, uncover," from PIE compound *ap-wer-yo- from *ap- "off, away" (see apo-) + root *wer- (4) "to cover." In optics, diameter of the exposed part of a telescope, microscope, etc., 1660s.

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*apo- 
also *ap-, Proto-Indo-European root meaning "off, away."

It forms all or part of: ab-; abaft; ablaut; aft; after; apanthropy; aperitif; aperture; apo-; apocalypse; apocryphal; Apollyon; apology; apoplexy; apostle; apostrophe; apothecary; apotheosis; awk; awkward; ebb; eftsoons; of; off; offal; overt.

It is the hypothetical source of/evidence for its existence is provided by: Sanskrit apa "away from," Avestan apa "away from," Greek apo "from, away from; after; in descent from," Latin ab "away from, from," Gothic af, Old English of "away from."
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*wer- (4)

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

It forms all or part of: aperitif; apertive; aperture; barbican; cover; covert; curfew; discover; garage; garment; garnish; garret; garrison; guarantee; guaranty; kerchief; landwehr; operculum; overt; overture; pert; warn; warrant; warrantee; warranty; warren; wat; Wehrmacht; weir.

It is the hypothetical source of/evidence for its existence is provided by: Sanskrit vatah "enclosure," vrnoti "covers, wraps, shuts;" Lithuanian užveriu, užverti "to shut, to close;" Old Persian *pari-varaka "protective;" Latin (op)erire "to cover," (ap)erire "open, uncover" (with ap- "off, away"); Old Church Slavonic vora "sealed, closed," vreti "shut;" Old Irish feronn "field," properly "enclosed land;" Old English wer "dam, fence, enclosure," German Wehr "defense, protection," Gothic warjan "to defend, protect."

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foramen (n.)
plural foramina, 1670s, from Latin foramen "hole, opening, aperture, orifice," from forare "to pierce" (from PIE root *bhorh- "hole").
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porthole (n.)

also port-hole, "aperture on a ship's side," originally especially one through which guns are fired, 1590s, from port (n.2) + hole (n.).

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shutter (n.)
1540s, "one who shuts" (see shut (v.)); meaning "movable wooden or iron screen for a window" is from 1680s. Photographic sense of "device for opening and closing the aperture of a lens" is from 1862.
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orifice (n.)

"an opening, a mouth or aperture," early 15c., from Old French orifice "the opening of a wound" (14c.) and directly from Late Latin orificium "an opening," literally "mouth-making," from Latin os (genitive oris) "mouth" (see oral) + combining form of facere "to make, do" (from PIE root *dhe- "to set, put"). Related: Orificial.

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embrasure (n.)
"enlargement of the interior aperture of a door or window," 1702, from French embrasure (16c.), from Old French embraser "to cut at a slant, make a groove or furrow in a door or window," from assimilated form of en- "in" (see en- (1)) + braser "to cut at a slant."
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open (n.)

early 13c., "an aperture or opening," from open (adj.). Sense of "an open or clear space" is by 1796. The open "open country" is from 1620s; as "open air" from 1875. Meaning "public knowledge" (especially in out in the open) is from 1942, but compare Middle English in open (late 14c.) "manifestly, publicly." The sense of "an open competition" is from 1926, originally in a golf context.

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dilatation (n.)

c. 1400, dilatacioun, "act of expanding, expansion," especially "abnormal enlargement of an aperture of the body," from Old French dilatation and directly from Late Latin dilatationem (nominative dilatatio) "a widening," noun of state from past-participle stem of Latin dilatare "make wider, enlarge," from dis- "apart" (see dis-) + lātus "broad, wide, widespread, extended" (see latitude). Also in Middle English "amplification in discourse" (late 14c.). In gynecology dilatation and curettage is by 1896.

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