In many languages the principal copula is a verb, like English "(to) be", German "sein", Mixtec "kuu", Touareg "emous", etc. It may inflect for grammatical categories like tense, aspect and mood, like other verbs in the language. Being a very commonly used verb, it is likely that the copula has irregular inflected forms; in English, the verb "be" has a number of highly irregular (suppletive) forms and has more different inflected forms than any other English verb ("am", "is", "are", "was", "were", etc.; see English verbs for details).