-al 1
a suffix with the general sense "of the kind of, pertaining to, having the form or character of" that named by the stem, occurring in loanwords from Latin ( autumnal; natural; pastoral ), and productive in English on the Latin model, usually with bases of Latin origin ( accidental; seasonal; tribal ). Originally, -al 1 was restricted to stems not containing an - l - (cf. -ar 1 ); recent lapses in this rule have produced semantically distinct pairs, as familiar and familial. Cf. -ical, ial .
[ alis, -ale; often r. ME -el ]
-al 2
a suffix forming nouns from verbs, usually verbs of French or Latin origin: denial; refusal.
[ -ale (sing.), -alia (pl.), nominalized neut. of -alis -AL 1 ; often r. ME -aille -alia ]
-al 3
Chem. a suffix indicating that a compound contains an aldehyde group: chloral.
[ presumed to be short for ALDEHYDE ]