Conditional forms
Conditional forms of verb are used to express if-then statements, or in response to counterfactual propositions (see subjunctive mood, above), denoting or implying an indeterminate future action.

Conditionals may be considered tense forms but are sometimes considered a verbal mood, the conditional mood.

Conditionals are expressed through the use of the verbal auxiliaries could, would, should, may and might in combination with the stem form of the verb.

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1. He could go to the store.
2. You should be more careful.
3. I may try something else.
4. He might be heading north.

Note that for many speakers, "may" and "might" have merged into a single meaning (that of "might") that implies the outcome of the statement is contingent. The implication of permission in "may" seems to remain only in certain uses with the second person, e.g. "You may leave the dinner table."

Two main conditional tenses can be identified in English:

I would think = Present Conditional
I would have thought = Conditional Perfect