A lipogram is a text that deliberately excludes one or more letters. The most famous example of a lipogram is the novel "La Disparition" by Georges Perec, which was written, in French, without using the letter "e" (and subsequently translated into English "A Void" by Gilber Adair, whilst retaining the constraint.)

Lipogam in a:

   To be or not to be: this is the question

Lipogram in e:

  Survival or oblivion: that is our quandry

Lipogram in t:

  Being or non-being: such is my dilemma