What is the Latin word for unfaithfully?

The usual Latin words for “unfaithfully” are perfidiōsus, perfidus, īnfidēlis; also Salvĭānus. The right choice depends on the sense; see the distinctions below.

English → Latin

“unfaithfully” in Latin

perfidiōsustreacherous, perfidious perfidusthat breaks one's promise; false; faithless; dishonest; disloyal; deceitful; treacherous; unsafe; dangerous īnfidēlisunfaithful; treacherous, disloyal; unbelieving, infidel Salvĭānusnamed from one Salvius

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

unfaithfully

perfidiose (Cic.); perfide (post-Augustan); infideliter (very late; Salvianus): ☞ infide not found.

Quick answer

What is the Latin word for unfaithfully?: The usual Latin words for “unfaithfully” are perfidiōsus, perfidus, īnfidēlis; also Salvĭānus. 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.