Verbs may also be affected by agreement, polypersonal agreement, incorporation, noun class, noun classifiers, and verb classifiers.[4] Agglutinative and polysynthetic languages tend to have the most complex conjugations, albeit some fusional languages such as Archi can also have extremely complex conjugation. Typically the principal parts are the root and/or several modifications of it (stems). All the different forms of the same verb constitute a lexeme, and the canonical form of the verb that is conventionally used to represent that lexeme (as seen in dictionary entries) is called a lemma.