What is the Latin word for illogical?

The usual Latin words for “illogical” are parum, quī. The right choice depends on the sense; see the distinctions below.

English → Latin

“illogical” in Latin

parumvery little; insufficient, not enough, too little quīwho, that, which, what

Riddle & Arnold A Copious and Critical English–Latin Lexicon, 1864

illogical

vitiose conclusus, or *minus or parum necessaria consecutione confectus (after Cic., Invent. 1, 29, 44): To draw an illogical inference, vitiose concludere (Cic.). This is most illogical arguing, haec dicuntur inconstantissime (Cic., Fin., 2, 27, 88). What can be more illogical, than? etc., quid autem est inscitius, quam? etc. (Cic., N.D., 2, 13, 36): that is an illogical conclusion, illud minime consectarium (Cic.).

Quick answer

What is the Latin word for illogical?: The usual Latin words for “illogical” are parum, quī. The right choice depends on the sense; see the distinctions below.

Entry from J. E. Riddle & T. K. Arnold, A Copious and Critical English–Latin Lexicon (rev. C. Anthon, New York: Harper, 1864), digitised by Fergus J. P. Walsh, CC BY-SA 4.0; Latin markup adapted by latindictionary.co.