Dual pronouns

In the Finnish, some pronouns are dual in the sense of referring to exactly two or to one of exactly two. In English, the pronoun “both” is of this type. Finnish has some more:

• the pronouns kumpikin and molemmat, cor­re­spond­ing to English “both”
• kumpikaan, the negative-context variant of kumpikin
• the pronoun jompikumpi, meaning “either of the two”
• the interrogative pronoun kumpi (which of the two)
• the use of toinen when referring to one of a set

In applicable contexts, the use of one of these pronouns is obligatory when referring to a known set of two. For example, the English phrase “one of them”, when referring to people, needs to be translated as toinen heistä or jompikumpi heistä when “they” are two people, otherwise as yksi heistä or joku heistä.

The pronoun molemmat is plural in form and treated as plural in congruence, e.g. molemmat miehet (both men), molemmat ovat (they both are). Other dual pronouns are treated as singular, even kumpikin, e.g. jompikumpi mies (either of the two men), kumpikin on (we/you/they both are).