Using the Subjunctive Mood To Indicate Uncertainty

One common purpose of the subjunctive mood is to indicate uncertainty. This can be done in Spanish even in cases where the English translation would be ambiguous.

For example, take an English sentence such as "I didn't know she studied Spanish." This could be translated into Spanish in at least two different ways, but the meaning differs:

• Yo no sabía que María estudiaba español. The dependent clause here (que estudiaba ...) is in the indicative mood. As such, it indicates certainty on the speaker's part that María actually studied Spanish. In effect, the speaker is saying, I didn't know that María studied Spanish, but now I do.
• Yo no sabía que María estudiara español. The dependent clause here (que estudiara ...) is in the subjunctive mood. This indicates some uncertainty on the speaker's part as to whether María studied Spanish. In effect, the speaker is saying, I didn't know that María studied Spanish, and I'm still not sure.

In the same way, the use of the subjunctive can indicate some hesitation or doubt on part of the speaker:

• Parece que es un error de computadora. The speaker is indicating that the problem appears to be a computer error. As in this example, forms of parecer are typically followed by a verb in the indicative mood.
• Parece que sea un error de computadora. This sentence could be translated the same as the above one: "It seems that it is a computer error." But by using the subjunctive, the speaker is expressing hesitancy about her conclusion.

In most cases, the use of the subjunctive is mandated by the structure of the sentence. But in some cases, such as these above, the choice of the indicative or subjunctive mood can express a nuance of meaning that may not be evident in the English translation.