-t-

From the -t of Latin -et, -it, which survived in Old French in some verb forms, now still spelt with -t (such as il fait, dort etc.). In Middle French, when final /t/ was no longer pronounced outside of liaison, the ending was reinstated analogically in the inversion forms of all verbs, even those in which -t had already been lost in Old French. (Note, however, that verbs with final -t, -d can make liaison generally before a vowel, while the others do so in inversion only.)

• IPA^(key): /t/

-t-

1. an interfix, liaison or linking consonant used in inversion constructions for third-person singular verbs with orthographic forms ending in a letter other than -t or -d
   • 1965 November, Carlo François, “Poésie d’André Marissel [André Marissel’s Poetry]”, in The French Review, volume 39, number 2, American Association of Teachers of French, JSTOR 384814, pages 265–274:

     Le jardinier-poète sait parfois qu’il est fécond et que son Arbre est fertile. Ne vainc-t-il pas la mort chaque fois qu’il plante un arbre-poème?

     (please add an English translation of this quote)

   Parle-t-on? ― Are we talking?

   Me regarde-t-il ? ― Is he looking at me?

   Y a-t-il un endroit? ― Is there a place?

   Quelles baleines Claire a-t-elle vues?

   Which whales did Claire see?

2. added between vowels to prevent certain sequences of vowels

   Coordinate term: -l-

   biffeton, dépiauter, gruter, maintée

Euphonic linking sound.

• IPA^(key): /t/

-t-

1. Used to separate two adjacent sonorants, mostly when -en is followed by -lich.

   Wesen + -t- + -lich → wesentlich

   eigen + -t- + -lich → eigentlich

-t-

1. joiner used with some nouns in noun incorporation