Porque is followed by a subjunctive when it is preceded by a negative.
Lo hago no porque me lo pidas, sino porque quiero.
I’m not doing it because you ask me to, but because I want to.No porque sea mi jefe voy a aceptar lo que me ha hecho.
I’m not going to accept what he’s done just because he’s my boss. 18.1.5 (p. 85)
Pues is often used in colloquial speech in place of porque. This use is especially
common in Spain.
No vine porque/pues me dolía la cabeza.
I didn’t come because I had a headache.Hice de intérprete porque/pues no hablaba español.
I acted as an interpreter because he/she didn’t speak Spanish.Porque and pues are not always interchangeable so, unless you are sure, you are
advised to use porque.43.2.2 Por... , a causa de... and debido a... can be used in similar contexts. The first one is
more colloquial and more common in the spoken language. The other two are slightly
more formal and used in the spoken as well as the written language.
Lo he escondido por los chicos.
I have hidden it because of the children.
Por la lluvia no pudimos venir.
Because of the rain we couldn’t come.
El partido se suspendió a causa de/debido a la lluvia.
The game was cancelled because of/due to the rain.43.2.3 Se debe a... , from deberse a, ‘to be due to’, is used for giving reasons or expressing
relationships of cause and effect in more formal contexts, in writing as well as in the
spoken language.
Su actitud se debe a ignorancia.
His/her attitude is due to ignorance.
El retraso se debió al mal tiempo.
The delay was due to bad weather.43.2.4 Como... introduces a reason, containing information which is new or known to the
listener, followed by a clause which explains the effect. Como is placed at the
beginning of the sentence.
Como no viniste ayer, hoy tendrás que quedarte hasta más tarde.
As you didn’t come yesterday, today you’ll have to stay until later.
Como no habla español no pudieron darle el puesto.
As he/she doesn’t speak Spanish they couldn’t give him/her the job.43.2.5 Ya que... and puesto que... introduce a reason containing information relevant to
the context or to the listener. These two expressions are interchangeable and they tend
to be used in more formal contexts, especially in writing. Ya que... is overall more
Giving reasons and expressing relationships of cause and effect 43.2