-al1

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, -al1 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.
Compare -ical, -ial
Origin
< Latin ālis, -āle; often replacing Middle English -el < Old French

-al2

1.
a suffix forming nouns from verbs, usually verbs of French or Latin origin:
denial; refusal.
Origin
< Latin -āle (singular), -ālia (plural), nominalized neuter of -ālis -al1; often replacing Middle English -aille < Old French < Latin -ālia

-al3

1.
Chemistry. a suffix indicating that a compound contains an aldehyde group:
chloral.
Origin
presumed to be short for aldehyde
British Dictionary definitions for -al

-al1

suffix
1.
of; related to; connected with: functional, sectional, tonal
Word Origin
from Latin -ālis

-al2

suffix
1.
the act or process of doing what is indicated by the verb stem: rebuttal, recital, renewal
Word Origin
via Old French -aille, -ail, from Latin -ālia, neuter plural used as substantive, from -ālis-al1

-al3

suffix
1.
indicating an aldehyde: ethanal
2.
indicating a pharmaceutical product: phenobarbital
Word Origin
shortened from aldehyde
Word Origin and History for -al

suffix forming adjectives from nouns or other adjectives, "of, like, related to," Middle English -al, -el, from French or directly from Latin -alis (see -al (2)).

suffix forming nouns of action from verbs, mostly from Latin and French, meaning "act of ______ing" (e.g. survival, referral), Middle English -aille, from French feminine singular -aille, from Latin -alia, neuter plural of adjective suffix -alis, also used in English as a noun suffix. Nativized in English and used with Germanic verbs (e.g. bestowal, betrothal).

word-forming element in chemistry to indicate "presence of an aldehyde group" (from aldehyde). The suffix also is commonly used in forming the names of drugs, often narcotics (e.g. barbital), a tendency that apparently began in German and might have been suggested by chloral (n.).

-al in Medicine

-al 3
suff.
Aldehyde: butyral.