This document discusses negation in English sentences. It explains that to negate a sentence with an auxiliary verb, "not" is added after the auxiliary verb. To negate a sentence without an auxiliary verb, a form of "do" plus "not" is added after the subject. There are also non-assertive forms that do not occur naturally outside of negative, interrogative, or conditional clauses, such as "any", "yet", or "at all". Certain words like "seldom" and "rarely" are negative in meaning but not appearance and take non-assertive forms.