表示选择关系的连词：主要有or, either … or, or else, whether … or, otherwise等。如Which do you like better, tea or coffee?
Either you leave this house or I’ll call the police.
Do it at once, or else! = Do it at once, otherwise you will suffer in some way.
Take a taxi, otherwise you won’t get there in time.
表示因果推理关系的连词：主要有so, for, then, therefore等。
