Mientras with the present indicative or the present subjunctive in Spanish

The word "mientras" in Spanish introduces a subordinate clause that expresses an action that is taking place at the same time as another (while) or a condition that is needed to fulfil the action in the main clause (as long as).

Mientras with the present indicative

Let's see some examples:

These examples above are using "mientras" followed by El Presente and it is translated as "while".

Mientras with the present subjunctive

Let's see some examples:

Here we're using "mientras" followed by El Presente de Subjuntivo and it is translated by "as long as". 

Let's see the difference between these two nearly identical sentences:

In the first example where we use El Presente (preparas) there are two actions happening at the same time (watching his favourite programme and making dinner).

In the second sentence where we use El Presente de Subjuntivo (prepares), the action in the main clause (watching his favourite programme) happens only if the condition expressed with "mientras" is fulfilled (only if he makes dinner).

Here is another example to compare:

In the sentence above two actions happen at the same time (El Presente)

Here, there is a condition to fulfil the action (El Presente de Subjuntivo )

Note:

Sometimes, in sentences using the future tense in the main clause, mientras could also mean while when followed by the subjunctive. In this case, we will be talking about two actions that may happen at the same time. For example:

The meaning of this sentence could be:

1. Lola will dance as long as we sing. (only if we sing she will dance)

2. Lola will dance while we sing. (for as long as/while we sing she will dance -two possible actions happening at the same time)