Learn Spanish (Latin America): Necesitas leer para que asimiles el vocabulario. - You need to read so that you assimilate the vocabulary.

Usually, when the subject is the same for both actions ('you' need to read and 'you' assimilate), Spanish speakers prefer para + infinitive: para asimilar. However, using para que is still correct here and is sometimes used to put a slightly stronger emphasis on the specific outcome. Just remember that adding que forces you to use the subjunctive mood.

Why is asimilar conjugated in the subjunctive mood (asimiles) here?

Because it directly follows para que (so that). In Spanish, para que always triggers the subjunctive mood. This is because it introduces a purpose or a goal, which is a future idea that hasn't been achieved yet, rather than a stated reality.

Why can't I use porque instead of para que in this sentence?

Porque means 'because' and explains the cause or reason behind an action (e.g., you read because you have a test). Para que means 'so that' and explains the purpose or goal of the action. Since absorbing the vocabulary is the goal of reading here, you need para que.

Is asimilar a common word to use when talking about vocabulary?