Using porque, como and es que to express cause (subordinate causal clauses)

There are many different types of conjunctions in Spanish that express a "cause". Here are three common ones, but they work in slightly different ways:

Porque

With porque we explain the cause of something:

Hoy no voy al trabajo porque estoy enfermo.I am not going to work today because I am ill.

El profesor está enfadado porque los estudiantes charlan en clase continuamente.The teacher is angry because the students chat in class continuously.

Me he puesto morena porque he estado en Tenerife una semana.I got a tan because I was in Tenerife for a week.

The normal order in this type of sentences with porque is: 

  1. Consequence first: "Hoy no voy al trabajo"
  2. Cause second: "porque estoy enfermo"

Como

With como we can also express a cause. Let's use the same examples as above but using como:

Como estoy enfermo, no voy a ir al trabajo hoy.As (because) I am ill, I am not going to work today.

Como los estudiantes charlan continuamente, el profesor está enfadado.As the students chat continuously, the teacher is cross.

Como he estado en Tenerife una semana, me he puesto morena.As I was in Tenerife for a week, I got a tan.

The normal order in this type of sentences with como is:

  1. Cause first: "Como he estado en Tenerife una semana"
  2. Consequence second: "me he puesto morena"

The parts must be separated by a comma.

Es que

With es que we introduce a cause which is often at the same time a "justification or an excuse" for doing something or having done something.

-Alberto, ¿qué te pasa? ¿Estás enfadado? -Es que mis estudiantes hablan continuamente en clase.-Alberto, what's the matter? are you cross? -The problem is my students chat continuously in class.

-Alberto, hoy no has ido a trabajar. -No, es que estoy enfermo.Alberto, you haven't been to work today. -No, the thing is I am ill.

-Alberto, estás muy moreno. -Es que he estado en Tenerife una semana.-Alberto, you are tanned. -Well, I was in Tenerife for a week.

Notice how the cause or excuse is given in the second sentence with es que, and it is an independant clause to the first one.

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Examples and resources

-Alberto, estás muy moreno. -Es que he estado en Tenerife una semana.-Alberto, you are tanned. -Well, I was in Tenerife for a week.
El profesor está enfadado porque los estudiantes charlan en clase continuamente.The teacher is angry because the students chat in class continuously.
Hoy no voy al trabajo porque estoy enfermo.I am not going to work today because I am ill.
Me he puesto morena porque he estado en Tenerife una semana.I got a tan because I was in Tenerife for a week.
Como estoy enfermo, no voy a ir al trabajo hoy.As (because) I am ill, I am not going to work today.
Como los estudiantes charlan continuamente, el profesor está enfadado.As the students chat continuously, the teacher is cross.
Como he estado en Tenerife una semana, me he puesto morena.As I was in Tenerife for a week, I got a tan.
-Alberto, ¿qué te pasa? ¿Estás enfadado? -Es que mis estudiantes hablan continuamente en clase.-Alberto, what's the matter? are you cross? -The problem is my students chat continuously in class.
-Alberto, hoy no has ido a trabajar. -No, es que estoy enfermo.Alberto, you haven't been to work today. -No, the thing is I am ill.
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