lyhentyvään
lyhentyvään is the genitive past passive participle of the Finnish verb lyhentyä. Lyhentyä itself means "to shorten" or "to become shorter." Therefore, lyhentyvään describes something that was in the process of shortening or had become shorter, viewed in relation to something else.
The genitive case in Finnish often indicates possession or a relationship. In the context of a participle,
The past passive participle form indicates an action that has been completed or is in a state