Échoir is a defective verb. It can not be conjugated in all possible forms.
Here are several examples of defectives verbs:
paître.
Échoir is conjugated in interro-negative form. The interro-negative form being obtained by inversion of the subject, the placement of the negative adverb follow the same rules as in negative form, giving the following rules:
- in interro-negative form, the adverb
« ne » is always placed first if the subject is a pronoun.
- in simple tenses, the adverbs (
« ne ...pas »,
« ne...plus »,
« ne...jamais », etc...) surround the verb
échoir and the inverted subject pronoun.
- in compound tenses or in ive voice, the negative adverbs surround the auxiliary and the inverted subject pronoun.
For sound reasons, like in interrogative form, an euphonious
« t » is added to the pronoun of the third person:
« il »,
« elle »,
« on »,
« ils »,
« elles » except when the verb ends with
« t » or
« d »:
« n'échoira-t-elle pas ">« n'aura-t-elle pas échu ? ».
Finally, the interrogative form does not exist in subjunctive and imperative.