chiyuv

An obligation.

When you're engaged, you have a chiyuv to set up your friends too. You might not have anybody in mind for your friends before you're engaged, but once you are, you obtain a special power that makes it possible to sense a good shidduch when you see one.

When it comes to a person's freedom of action in Judaism, there are only chiyuvim and issurim, and everything else is up to the individual.

A mourner who is obligated to say Kaddish.

When I was a chiyuv (saying kaddish for my father, a'h, and thus leading prayers almost every day), I asked my LOR whether I should continue my practice, or adopt the more standard version. He told me that my version was an acceptable variant within the shul's own accepted nusach.