Kenneth G. Wilson (1923–). The Columbia Guide to Standard American English. 1993.
irreligious, nonreligious, not religious, unreligious (adjs.)
To be irreligious means “to lack religion or to be heedless of it”; it suggests, however, a deliberate posture, not an inadvertent one. Nonreligious is matter of fact, simply an opposite of religious, meaning “secular.” Unreligious may be a synonym of either irreligious or nonreligious, but its overtones suggest the overtness or deliberateness we find in irreligious. In the predicate adjective position, not religious is matter of fact and closer in meaning to nonreligious. See also SACRILEGE.
