apt

First recorded in 1350–1400; Middle English, from Latin aptus “fastened, fitted, fitting, appropriate,” equivalent to ap(ere) “fasten, attach” + -tus past participle suffix

4. Apt, pertinent, relevant all refer to something suitable or fitting. Apt means to the point and particularly appropriate: an apt comment. Pertinent means pertaining to the matter in hand: a pertinent remark. Relevant means directly related to and important to the subject: a relevant opinion.

Some usage guides insist that apt followed by an infinitive can or should be used to mean only “inclined, disposed”: He is apt to ignore matters he regards as unimportant. In fact, apt is standard in all varieties of speech and writing as a synonym for likely in contexts that suggest probability without any implication of a natural disposition toward: Hostilities are apt to break out if the confrontation is not soon resolved. She is apt to arrive almost any time now. See also liable, likely.

First recorded in 1900–05