Think (verb)

1. To form an opinion or conclusion about something based on consideration or evidence.
2. To consider carefully.
3. To reflect on or ponder over something.
4. To plan or devise a strategy.
5. To expect or believe something to be the case.

Origin:

Middle english thenken, from old english thyncan; akin to old high german denken to think.

Examples:

1. I think it's going to rain today.
2. I need to think about it.
3. She thinks she's right.
4. I've been thinking about this for a while.
5. I'm thinking of going to the beach.