lukkoon

Lukkoon is a Finnish language form that functions as a complement indicating the act or result of locking something. It derives from the noun lukko (lock) and the illative/into-form suffix -koon, and it is most commonly used with verbs that describe securing or setting a lock.

In everyday use, lukkoon appears in phrases that command or describe the action of locking. Common constructions include laita tai pane ovi lukkoon, meaning “lock the door,” or “put it, lock it.” The form can also appear in past-tense or passive contexts to emphasize that something has been secured, for example, “ovi on laitettu lukkoon” (the door has been locked).

Lukkoon contrasts with related forms such as lukossa and lukittu. Lukossa means “in a locked state” or “locked,” as in ovi on lukossa (the door is locked). Lukittu is the past participle meaning “locked” as a descriptive adjective, as in ovi on lukittu. Lukkoon, by contrast, is oriented toward the action of locking or the state resulting from that action, often translating to “lock it” or “into a lock” in a literal sense.

Etymologically, lukkoon combines lukko with the illative suffix -koon, a pattern used in Finnish to express motion into a state or place. The form is standard in written and spoken Finnish and appears in both instructional language and descriptive prose.

See also: lukko, lukossa, lukittu, illative case.