I've seen infinitives function in a few different ways.
But in which ways can they function? I've seen infinitives function as direct objects, subjects, and a couple other ways, but how else can they act?
Some example sentences that I'm not sure how they're functioning:
"I don't know where to go" "The books to return are right here" "Emergency Room physicians struggle to prevent their own depression and burnout."
P.S I've heard infinitives for example act like complements and also modifiers, but what does this mean? (an example sentence would help)
And as a separate question: I was confused in these sentences how the subordinate clauses are functioning, although they aren't infinitivial
They have tons of speed and talent around him that can help him make big plays.
It’s so heavy that you can’t pick it up