In
Finnish,
jk is the
abbreviation for the word
jokin, meaning
something.
Who cares?
Well... Finnish is an
inflected language, in that
nouns (and
adjectives) have many
cases according to their use in a
sentence.
Genitive denotes possession;
Partitive denotes an unknown quantity and so on.
In a
dictionary, an abbreviation of
jokin will appear in the correct case for a given verb.
For example,
pitää (to
like something) takes the
Elative case, which normally denotes motion out of something, but in this case is just the
object of your
affection.
Se menee talosta - He goes out of the house.
but
Se pitää kahvista - He likes coffee.
So, in a dictionary, pitää would appear as "pitää (jstk)" to show that
pitää jostakin is "to like something".
There follows a list of cases with abbreviations, and full version:
It is possible to learn
Finnish for many years without this little
piece of
knowledge, but it gets much
easier once you know it.
Source:
http://www.uta.fi/~km56049/finnish/jkabb.html