With regular classes seen in Language note there exist two other classes that consist of nouns with a u- (w-) prefix in the singular and ma- or n- in the plural, that is, they belong to the subclasses [ma-ya] or [n-zi] in the plural. In some contexts, the infinitive form of the verb in Swahili corresponds to the English gerund. Like any other noun, the Swahili infinitive may serve as the subject of a conjugated verb and trigger an agreement prefix among pronouns and adjectives. The infinitive constitutes a noun class characterized by the nominal and pronominal prefix ku-. These nouns are considered members of subclass in the singular because their agreement patterns are the same as those of the non-animate nouns with a mu- prefix in the singular. Similar to other object pronouns, the vowel of the object pronoun -ji- is maintained before the stem vowel. The reflexive pronoun ji- is also used idiomatically with some verbs.