illogical

The word 'illogical' is a direct negation of 'logical', constructed within English. Its core, 'logic', descends from the Greek 'logikē', pertaining to reason or discourse, itself derived from 'logos' meaning "word, reason, principle". The Latin negative prefix 'in-' (meaning "not") assimilates to 'il-' before an 'l' for phonetic ease. The adjectival suffix '-al' is a common Latin-derived ending. Thus, the literal construction "not relating to reason" perfectly captures the modern meaning of lacking sound reasoning or sense.

Structure: il (not) + logic (reason) + al (adjective suffix) - il: Latin origin, a variant of the prefix 'in-' meaning "not". Its functional role is negation. - logic: Greek origin, from 'logikē' (tekhnē) meaning "(art) of reason". Its functional role is the core root denoting reason or rational thought. - al: Latin origin, adjectival suffix '-alis'. Its functional role is to form adjectives meaning "of, relating to, or characterized by".