“Ellipsis: The omission of an element of language for reasons associated with speech, rhetoric, grammar, and punctuation. The omitted element can usually be recovered by considering the context of what has been said or written, In speech and writing, sounds and letters are often left out of words: in the sentence She said he’d come, he’d is elliptical for either he had or he would. Such contractions are informal and usually arise from speed of delivery, economy of effort, and the rhythm of the language. At times, elliptical speech or writing is so concise that listeners and readers must supply missing elements through guesswork or special knowledge, but it they cannot, they fail to understand. Information can be left out or hinted at for reasons of style or discretion; in such areas as politics, diplomacy, and negotiation, remarks are often elliptical in nature and intent….”
Excerpted from: McArthur, Tom. The Oxford Concise Companion to the English Language. New York: Oxford University Press, 2005.