Ellipsis (or elliptical construction ) is the omission of a word or words. It refers to constructions in which words are left out of a sentence but the sentence can still be understood.

Ellipsis helps us avoid a lot of redundancy. In fact there is a lot of redundancy in language and it can be surprising how much can be left out without losing much meaning, particularly when there are contextual clues as to the real meaning.

Examples:

1. She can help with the housework; Nancy can (help with the housework), too.

2. John can speak seven languages, but Ron can speak only two (languages).

The words between parentheses can be omitted and the sentences can still be meaningful.