(archaic) Singular second person prevocalic possessive determiner (preconsonantal form: thy).

(archaic) Singular second person possessive pronoun; yours

That which is considered to exist as a separate entity, object, quality or concept. / A word, symbol, sign, or other referent that can be used to refer to any entity.

(rare) To express as a thing; to reify.

(transitive) To ponder. / (transitive) To consider as a course of action.

To create in one's mind; to originate an idea through thought. / Used other than figuratively or idiomatically: see think, of. (to think on the subject of)

(idiomatic) To be deluded, to be mistaken; to need to rethink something one has determined; to need to reconsider one's plans or expectations.

(idiomatic, especially US) Alternative form of have another think coming

I believe that is the case, but am not certain.

I think what has been said is untrue. / (sarcastic) No, absolutely not (used to refuse or decline something proposed).