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.

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

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.

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.

mid-13c., "an opening, an aperture;" early 15c. as "an introductory proposal, something offered to open the way to some conclusion," from Old French overture "opening; proposal" (Modern French ouverture), from Latin apertura "opening," from aperire "to open, uncover" (see overt).

The orchestral sense of "a movement serving as a prelude or introduction to an extended work" in English is recorded from 1660s.

1640s, "right as opposed to left," from Medieval Latin dexteralis "on the right," from Latin dexter "right, opposite of left," from PIE root *deks-. From 1871 as "right-handed." By 1818 in reference to univalve shells, "having the aperture on the right side when held upright in front of the observer with the apex upward." Related: Dextrally; dextrality.