early 15c., "an undertaking," formerly also enterprize, from Old French enterprise "an undertaking," noun use of fem. past participle of entreprendre "undertake, take in hand" (12c.), from entre- "between" (see entre-) + prendre "to take," contraction of prehendere "to catch hold of, seize" (from prae- "before," see pre-, + -hendere, from PIE root *ghend- "to seize, take"). Abstract sense of "adventurous disposition, readiness to undertake challenges, spirit of daring" is from late 15c.

late 15c., "to keep up, maintain, to keep (someone) in a certain frame of mind," from Old French entretenir "hold together, stick together, support" (12c.), from entre- "among" (from Latin inter; see inter-) + tenir "to hold" (from Latin tenere, from PIE root *ten- "to stretch").

Sense of "have a guest" is late 15c.; that of "gratify, amuse" is 1620s. Meaning "to allow (something) to consideration, take into the mind" (of opinions, notions, etc.) is 1610s. Related: Entertained; entertaining.

late 14c., "the highest faculty of the mind, capacity for comprehending general truths;" c. 1400, "faculty of understanding, comprehension," from Old French intelligence (12c.) and directly from Latin intelligentia, intellegentia "understanding, knowledge, power of discerning; art, skill, taste," from intelligentem (nominative intelligens) "discerning, appreciative," present participle of intelligere "to understand, comprehend, come to know." This is from assimilated form of inter "between" (see inter-) + legere "choose, pick out, read," from PIE root *leg- (1) "to collect, gather," with derivatives meaning "to speak (to 'pick out words')."

The meaning "superior understanding, sagacity, quality of being intelligent" is from early 15c. The sense of "information received or imparted, news" is recorded by mid-15c., especially "secret information from spies" (1580s). The meaning "a being endowed with understanding or intelligence" is late 14c. Intelligence quotient is recorded by 1921 (see I.Q.).

Latin, literally "amongst other things." from inter "among, between" (see inter-) + alia, neuter accusative plural of alius "(an)other" (see alias (adv.)). Latin for "among other persons" is inter alios.

"act on each other, act reciprocally," 1805, from inter- + act (v.). Related: Interacted; interacting.

"mutual or reciprocal action, influence of things on each other," 1807, from inter- + action.

"between two rivers" (usually, if not exclusively, with reference to Mesopotamia), 1774, from Late Latin interamnius, from inter "between" (see inter-) + amnis "a river," a word perhaps of Celtic origin (see afanc).

"intermingle," 1823, from inter- + blend (v.). Related: Interblended; interblending.

1803 (transitive) "to breed by crossing species or varieties," from inter- + breed (v.). Intransitive sense of "procreate with one of a different species" is from 1825. Related: Interbred; interbreeding.

"to insert a day into the calendar," 1610s, from Latin intercalatus, past participle of intercalare "to proclaim the insertion of an intercalary day," from inter "between" (see inter-) + calare "to call" (an intercalary day; see calendar). Sometimes used in a general sense, "to insert between others" (1824). Related: Intercalated; intercalating.

A necessary process in the Roman calendar to balance the solar and lunar aspects of it. Intercalation was done after Feb. 23 or 24 (the terminalia), every two or four years. Twenty-seven days were intercalated, making a full intercalary month (which included the last four or five days of Februarius), known as mensis intercalaris (and also known, according to Plutarch, as Mercedonius). No one now knows why the intercalation was done in the middle of February rather than after its end, unless it was because the important festivals at the end of that month (Regifugium and Equirra) were closely associated with holidays in early March. After Caesar's reform (46 B.C.E.) the only intercalary day is Feb. 29 every four years.