mid-15c., averten "to turn (something) aside" (the mind, the attention, etc.), from Old French avertir (later advertir) "to turn, direct; turn aside; make aware, inform" (12c.), from Latin advertere "turn toward, turn to," from ad "toward" (see ad-) + vertere "to turn" (see versus). The -d- was restored in English 16c. Especially in speaking or writing, "turn to (a topic) abruptly and plainly" (18c.). Related: Adverted; adverting.

late 15c., "informed;" 1780s, "publicly announced," past-participle adjective from advertise.

early 15c., "written statement calling attention to (something), public notice" (of anything, but often of a sale); from Old French avertissement (15c., later respelled pedantically as advertissement, a change rejected in French but accepted in English), from stem of avertir "to turn, direct, make aware" (see advertise). Meaning "public notice (usually paid) in a newspaper or other publication," the main modern sense, emerged 1580s and was fully developed by 18c.; later extended to Web sites.

Advertisements are now so numerous that they are very negligently perused, and it is therefore become necessary to gain attention by magnificence of promises and by eloquence sometimes sublime and sometimes pathetick. Promise, large promise, is the soul of an advertisement. I remember a washball that had a quality truly wonderful—it gave an exquisite edge to the razor! ... The trade of advertising is now so near to perfection that it is not easy to propose any improvement. [Johnson, "The Idler," Jan. 20, 1758]

mid-15c., in legal phraseology, denoting action of one party against another, from Latin versus "turned toward or against," past participle of vertere "to turn" (from PIE root *wer- (2) "to turn, bend").

late 14c., "attention, heed, act of calling attention to," from Old French avertence, avertance, from Late Latin advertentia "attention, notice," abstract noun from past participle stem of advertere "direct one's attention to; give heed," literally "to turn toward" (see advertise).

1560s, "one who notifies," agent noun from advertise (v.). From 1712 as "one who issues public notice," hence its use as a name for newspapers or journals (1769).

1590s, "criticism, blame, reproof; a critical commentary," also sometimes in early use simply "notice, attention, perception of an object" (a sense now obsolete), from Latin animadversionem (nominative animadversio) "investigation, inquiry; perception, observation," noun of action from past-participle stem of animadverte "to take cognizance of," literally "to turn the mind to," from animum, accusative of animus "the mind" (see animus), + advertere "turn to" (see advertise).

The sense of "take notice of as a fault" also was in Latin and animadverto at times was a euphemism for "to punish with death."

early 15c., animadverten, "to take notice of," from Latin animadvertere "to notice, take cognizance of," also "to censure, blame, punish," literally "turn the mind to," from animus "the mind" (see animus) + advertere "turn to" (see advertise). The sense of "to criticize, blame, censure" in English is attested from 1660s. Related: Animadverted; animadverting.

"carelessness, negligence, inattention," mid-15c., from Old French inadvertance "thoughtlessness, heedlessness" (14c.), from Scholastic Latin inadvertentia, from in- "not" (see in- (1)) + advertentia, from Latin advertere "to direct one's attention to," literally "to turn toward" (see advertise).

word-forming element expressing direction toward or in addition to, from Latin ad "to, toward" in space or time; "with regard to, in relation to," as a prefix, sometimes merely emphatic, from PIE root *ad- "to, near, at."

Simplified to a- before sc-, sp- and st-; modified to ac- before many consonants and then re-spelled af-, ag-, al-, etc., in conformity with the following consonant (as in affection, aggression). Also compare ap- (1).

In Old French, reduced to a- in all cases (an evolution already underway in Merovingian Latin), but French refashioned its written forms on the Latin model in 14c., and English did likewise 15c. in words it had picked up from Old French. In many cases pronunciation followed the shift.

Over-correction at the end of the Middle Ages in French and then English "restored" the -d- or a doubled consonant to some words that never had it (accursed, afford). The process went further in England than in France (where the vernacular sometimes resisted the pedantic), resulting in English adjourn, advance, address, advertisement (Modern French ajourner, avancer, adresser, avertissement). In modern word-formation sometimes ad- and ab- are regarded as opposites, but this was not in classical Latin.