A headword, head word, lemma, or sometimes catchword is the word under which a set of related dictionary or encyclopaedia entries appear. The headword is used to locate the entry, and dictates its alphabetical position. Depending on the size and nature of the dictionary or encyclopedia, the entry may include alternative meanings of the word, its etymology and pronunciation, compound words or phrases that contain the headword, and encyclopedic information about the concepts represented by the word.