5.6: §36. The Latin suffix -ILIS (> E -ile or -il)
In contrast to the huge category that we have just met, there is a rather small number of Latin adjectives formed by adding the suffix -īlis to the noun base. These regularly appear in English as words ending in – ile , occasionally in – il . Most conspicuous, perhaps, are the adjectives relating to the periods of human life (especially, a man’s life). The Latin word for a baby was infans, infant-is ; “like a baby” was infant-ilis , whence English infantile . Because “boy” was puer (a 2nd declension subtype), “boyish” was puer-ilis (E puerile) . From juvenis (“young man”) came juven-ilis (E juvenile). The noun vir (“man”) produced the adjective vir-ilis (E virile) , and senex, sen-is (“old man”) yielded sen-ilis (E. senile) . There was also a Latin adjective to describe an old woman— anilis , from the noun ă nus (pronounced differently in Latin from ānus [E anus ], a word that the Romans considered crude). There does exist an English word anile (“like an old woman”), but its rareness is probably the result of its similarity to anal (< analis , < ā nus ).
Outside of this coherent little group, there are only a few important – ilis derivatives of this type in English: servile (“like a slave”) < servilis < servus ; hostile (“like an enemy”) < hostilis < hostis ; civil (“pertaining to a citizen”) < civilis < civis ; and gentile (“pertaining to the nations”) < gentilis < gens, gent-is (“clan,” “race”). The last, of course, has had its English meaning specialized to “non-Jewish,” from the Biblical contrast between the Jews and the gentiles. Gentile has three rather curious DOUBLETS— gentle , genteel , and jaunty , all transmitted and influenced by French gentil .