In older forms of French, and in more formal registers of present-day French, the role of est-ce que is often fulfilled by subject-verb inversion:
Quand viendrez-vous ? ― When will you come?
In fact, est-ce que itself results from subject-verb inversion; it comes from c’est que — however, in modern French, est-ce que is a set phrase that does not necessarily function as the inversion of c’est que and the former can be used to introduce a question beginning with the latter:
Est-ce que c’est que les hommes sont partis ?
Have the men left?
In colloquial French, yes-or-no questions are often indicated solely by punctuation (in writing) or intonation (in speech), with no special lexical or syntactic marker:
T’es prête ? ― You ready?
Similarly, non–yes-or-no questions often use the same structure as statements, with question words not being preposed:
Il a dit quoi ? ― He said what?
In informal or colloquial French, question syntax is often used instead of subject-verb inversion in indirect questions:
