From Dictionary.com. I have highlighted the parts of the definition that speak to me.
Think
verb (used without object)
1. to have a conscious mind, to some extent of reasoning, remembering experiences, making rational decisions, etc.
2. to employ one's mind rationally and objectively in evaluating or dealing with a given situation: Think carefully before you begin.
3. to have a certain thing as the subject of one's thoughts: I was thinking about you. We could think of nothing else.
4. to call something to one's conscious mind: I couldn't think of his phone number.
5. to consider something as a possible action, choice, etc.: She thought about cutting her hair.
6. to invent or conceive of something: We thought of a new plan.
7. to have consideration or regard for someone: Think of others first.
8. to esteem a person or thing as indicated: to think badly of someone.
9. to have a belief or opinion as indicated: I think so.
verb (used with object)
11. to have or form in the mind as an idea, conception, etc.
12. to have or form in the mind in order to understand, know, or remember something else: Romantic comedy is all about chemistry: think Tracy and Hepburn. Can't guess? Here's a hint: think 19th century.
13. to consider for evaluation or for possible action upon: Think the deal over.
14. to regard as specified: He thought me unkind.
15. to believe to be true of someone or something: to think evil of the neighbors.
EXPAND
adjective
19. of or pertaining to thinking or thought.
20. Informal . stimulating or challenging to the intellect or mind: the think book of the year.
noun
21. Informal . the act or a period of thinking: I want to sit down and give it a good think.
Verb
phrases
22. think of,
a. to conceive of; imagine.
b. to have an opinion or judgment of.
c. to consider; anticipate: When one thinks of what the future may bring, one is both worried and hopeful.
23. think out / through,
a. to think about until a conclusion is reached; understand or solve by thinking.
b. to devise by thinking; contrive: He thought out a plan for saving time.
24. think up, to devise or contrive by thinking: Can you think up an arrangement of furniture for this room?
Idioms
25. think better of, to change one's mind about; reconsider: She considered emigrating to Australia, but thought better of it.
26. think fit, to consider advisable or appropriate: By all means, take a vacation if you think fit.
27. think nothing of. nothing ( def. 19 ) .
28. think twice, to weigh carefully before acting; consider: I would think twice before taking on such a responsibility.