A universal property of natural language is that every language is able to express negation, i.e., every language has some device at its disposal to reverse the truth value of the propositional content of a sentence. The syntax of negation is indissolubly connected to the phenomenon of (negative) polarity. The second section of this chapter deals with the syntax of negative markers, and the third section deals with the syntax and semantics of (negative) polarity items. The chapter focuses specifically on negative concord (i.e., the phenomenon where multiple instances of morphosyntactic negation yield only one semantic negation), with special emphasis on the ambivalent nature of n-words. The various studies of the syntactic properties of negative markers (most notably Zanuttini's analyses of negative markers in Romance varieties) led to a much better understanding of what constrains the cross-linguistic variation that languages exhibit with respect to the expression of sentential negation.