-acal

suffix forming adjectives, often used to distinguish them from nouns in -ac (heliacal; maniacal).

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suffix forming adjectives from nouns and adjectives usually ending in -ac, such as maniacal, often making a distinction from nouns ending in -ac (as in maniacal compared with maniac)

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-acal

compound suffix; consisting of -al¹ repr. L. -ālis, -āle ‘of the nature of, belonging to,’ added to -ac (q.v.), which although strictly an adj. ending was so often used substantively, e.g. demoniac, maniac, ammoniac, aphrodisiac, that it became usual to make the adj. in -acal even when no n. occurs, as heliacal. As in the cogn. -ic, -ical, adjectives in -ac are primary objective attributes, of or pertaining to the thing, while adjectives in -acal are only secondary, of the nature of or connected with the attribute in -ac, or its embodiment, hence more remotely and subjectively relating to the thing; e.g. the cardiac arteries, a cardiac (medicine), cardiacal qualities of a herb. But this distinction is not always observed. Examples: ammoniacal, aphrodisiacal, cardiacal, demoniacal, heliacal, hypochondriacal, maniacal, paradisiacal, prosodiacal, theriacal.