Some
conjunctions (those little words that connect two part
sentences) always (!!!) use the subjuntivo.
These conjunctions have in their "nature"
to express something unreal or uncertain. Again the
thumb rule works.
Se
lo he dicho para
que aprenda
lo que hay que hacer.
= I told him that he learns what (he has)
to do.
explanation:para que expresses
an intention, something that has not yet become
real
En
caso que venga,
le doy el dinero.
= In case he comes I give him the money.
explanation:
In case expresses clearly that it is still
uncertain that the guy is coming,
Hace
como si
ganara mucho dinero, pero la verdad es que
es tan pobre como nosotros.
= He pretends (direct translation: does as
if) he earned a lot of money, but in reality,
he is as poor as we are.