lukkoihin

Lukkoihin is the plural illative form of the Finnish noun lukko, which means lock. The illative case marks direction toward or into something, and the plural illative is used when the destination is more than one lock. The corresponding singular illative form is lukkoon, meaning “into the lock.” The plural illative form lukkoihin is formed by attaching the illative suffix to the stem lukko- and follows Finnish vowel harmony, with the typical realization of the suffix as -iin (resulting in lukkoihin).

In usage, lukkoihin appears in contexts involving several locks, such as descriptions of actions directed at multiple locks or discussions of security hardware that covers a set of locks. It is standard in technical, architectural, or security-related texts and precise descriptions, though in everyday speech speakers may use lukkoon when referring to a single lock.

Linguistically, lukkoihin is a case-inflected form rather than a separate lexical item. It demonstrates Finnish’s system of cases used to express direction, where the form of the noun changes to reflect its grammatical role in a sentence. See also lukko for the base noun.