It is only the aid of large corpora (several billions of words) that enables us to discover some intuitively and spontaneously followed rules of grammar. Different kinds of ellipsis and non-ellipsis (repetition of a word or a nominal phrase, which - under some conditions - can be omitted) can also be governed by such rules. The corpus findings of sentence structures as (1) Zastavila se a podívala se na hodinky or (2) Zastavila se a podívala na hodinky (She stopped and looked at her watch) have clearly shown that ellipsis as well as repetition is a (strict) rule under specific semantic and syntactic conditions.