私には先約があります。

I; me; private affairs; personal matter; secrecy; selfishness

at (place, time); in; on; during; to (direction, state); toward; into; for (purpose); because of (reason); for; with; by; from; as (i.e. in the role of); per; in; for; a (e.g. "once a month"); and; in addition to; if; although

topic marker particle; indicates contrast with another option (stated or unstated); adds emphasis

previous engagement; prior contract

indicates sentence subject (occasionally object); indicates possessive (esp. in literary expressions); but; however; still; and

to be (usu. of inanimate objects); to exist; to live; to have; to be located; to be equipped with; to happen; to come about