imprecise (adj.)

word-forming element meaning "not, opposite of, without" (also im-, il-, ir- by assimilation of -n- with following consonant, a tendency which began in later Latin), from Latin in- "not," cognate with Greek an-, Old English un-, all from PIE root *ne- "not."

In Old French and Middle English often en-, but most of these forms have not survived in Modern English, and the few that do (enemy, for instance) no longer are felt as negative. The rule of thumb in English has been to use in- with obviously Latin elements, un- with native or nativized ones.

mid-15c., "neither more nor less than, with no error; exactly stated or marked off; definitely or strictly expressed; distinguished with precision from all others," from Old French précis "condensed, cut short" (14c.) and directly from Medieval Latin precisus, from Latin praecisus "abrupt, abridged, cut off," past participle of praecidere "to cut off, shorten," from prae "before" (see pre-) + -cidere, combining form of caedere "to cut" (from PIE root *kae-id- "to strike"). For the Latin vowel change, see acquisition. Related: Precisely (late 14c.).