forms the conditional mood; would, would've

creates a subordinate clause expressing desire or wish; to, so that, for that, in order to [+past tense]
creates an optative clause; if only, had better, let [+past tense]
creates a subordinate clause expressing aim or purpose, one's goal; to, so that, for that, in order to [+infinitive]
creates a subordinate clause in which one states the possibility of something depends on something else; to, so that, for that, in order to [+infinitive]
introduces a subordinate clause relating a following event with a previous one that is not caused by the first event; just to, only to [+infinitive]
introduces a subordinate clause expression doubt; if