spontané

spontaneous, self-generated (happening without any apparent external cause); spontaneous, natural, unforced

“génération spontanée” — spontaneous generation

Learned borrowing from Late Latin spontāneus. In modern French, only words descending from Latin borrowings of Greek origin ending in the suffixes -ēus/-ēum, -aeus/-aeum (and exceptionally -ius/-ium, as in élysée/Élysée) are written with -ée in the masculine. Words descending from Latin words in -āneus (a different suffix, from -ānus + -eus), are now written with the ending -ané (as seen, for example, in méditerrané, momentané). The first four editions of the Dictionnaire de l'Académie française