Negative polarity refers to the linguistic phenomenon where certain expressions or words can only appear in negative contexts. For example, words like "any" or "ever" are often used in sentences that contain negation, such as "I don't have any money" or "I haven't seen him ever." These expressions are not typically used in positive statements. This concept is important in understanding how language functions, particularly in the realm of syntax and semantics. Negative polarity items help convey specific meanings and can influence the interpretation of sentences. Recognizing these patterns aids in grasping the nuances of grammar and effective communication.