Unavailable means not able to be used, obtained, or reached. When something is unavailable, it's simply not there when you need it, whether that's a person, an object, or an opportunity.

A library book might be unavailable because someone else checked it out. Your favorite item at a restaurant might be unavailable because they ran out of ingredients. A seat on a field trip bus could be unavailable because all the spots are already taken.

When a person is unavailable, they can't meet with you or help you right then. Maybe your teacher is unavailable during lunch because she has a meeting, or your friend is unavailable to play because he has a doctor's appointment. Being unavailable doesn't mean someone is avoiding you, just that they're busy or committed elsewhere.

The word often appears in everyday situations: a website shows that a product is temporarily unavailable, or a sign says the playground is unavailable for use during repairs. Sometimes people describe themselves as unavailable when they're too busy to take on new commitments, like a tutor who says she's unavailable for new students because her schedule is full. The opposite is available, meaning ready and accessible when needed.