Cause
Why does something happen or turn out this way?
Meaning
A cause explains why something happens or why a situation is as it is. It may be an earlier event, a circumstance, or someone's reason for acting. Languages use linking words, endings, or context, and some have no separate cause marker. Unlike Purpose, Cause explains what brings about an event, not what someone hopes to achieve.
How to spot it
Find the part that answers why the event happened or why the situation is as described.
In your native language
English uses because to introduce a reason expressed as a full clause, a part with its own subject and verb. Because of comes before a noun or a noun phrase, a group of words built around a noun. Since and as can also introduce reasons, though they have other meanings in other contexts.
I took a taxi because I was late.
Because introduces a reason with its own subject and verb.
The game was canceled because of the rain.
Because of is followed by a noun phrase, not a full clause.
Since the store is closed, we'll come back tomorrow.
Since gives a reason here; it does not mark a starting time.
In your learning language
Spanish introduces a reason stated as a whole event with porque. Por introduces a cause expressed as a noun or an infinitive, a verb form such as salir with no person ending. These forms explain what led to an event, rather than the goal commonly introduced by para.
No fuimos al parque porque llovía.
We didn't go to the park because it was raining.
La tienda está cerrada por vacaciones.
The store is closed for vacation.
Perdí el autobús por salir tarde de casa.
I missed the bus because I left home late.
Por introduces the action that caused the missed bus.
Learners whose language uses one form before both nouns and full statements may confuse por and porque, as in *por llovía. Learners whose language uses the same marker for a reason and a goal may also confuse por with para.