This paper purposes to identify and dissect ambiguous meanings involved in quantification and negation in a bid to help students realize that they should not be remiss in dealing with the meanings of quantifier and negation contexts. To this end, this paper focuses not only on the inherent properties of quantification but also on negation context in an English textbook. To stress that learners, when in high school in particular, need to build up ability to figure out the exact meaning of a sentence, this paper leads off with ambiguity triggered by quantification and negation phrases. To clarify quantification readings in the textbook, this paper reviews the predicate calculus for a logical significance and quantification specified by two kinds of quantifiers: existential and universal. This paper also investigate the use and frequency of quantification in terms of 10 quantifiers and negation in an English textbook.