What is the Latin word for inability?

The usual Latin words for “inability” are imbēcillitās, īnfirmitās. The right choice depends on the sense; see the distinctions below.

English → Latin

“inability” in Latin

imbēcillitāsweakness, feebleness; powerlessness, helplessness; illness īnfirmitāsweakness, feebleness, infirmity; sickness

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

inability

by circumlocution with facere aliquid non posse, etc.: or non potentem esse alicujus rei or ad aliquid faciendum. [Vid: INCAPABLE.] ☞ Impotentia can only be used either with a genitive, irae, animi, etc., in the sense of “inability to restrain one’s wrath, govern one’s temper,” etc., or absolutely, in the sense of “weakness,” hinc intelligitur... tacita impotentiae exprobratio, Quint., 6, 2, 16. Sometimes imbecillitas, infirmitas (weakness) may serve.

Inability to pay, by circumlocution with solvendo non esse; solvere non posse, non idoneum esse. Vid: SOLVENT.

Quick answer

What is the Latin word for inability?: The usual Latin words for “inability” are imbēcillitās, īnfirmitās. 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.