This chapter discusses the expressions often referred to as n-words. While this term has been used extensively in the literature, we use here the more neutral term ‘negative concord items’ (NCI) since these expressions do not always contain negation. NCIs behave largely as negative polarity items (NPIs) in requiring negation for grammaticality; and questions arise about whether or not they are semantically negative, and whether they are uniform across languages. The chapter shows that NCIs exhibit variation in their distribution and interpretation. Main aspects of variation are whether NCIs always require negation (strict negative concord), or not (non-strict), and whether they can appear with non-negative meanings. The chapter assesses research of the past twenty years, and proposes a new, more synthesized, understanding of the attested variation.