The conditional tense is used to describe what would happen under certain circumstances. It is one of the two tenses that describe upcoming events or situations. In English it could be translated as would + verb. It is formed by adding the endings of the –er and –ir imperfect tense verbs to the infinitive.

Note:
The conditional tense uses the same modified infinitive form as the future tense.
reduced infinitives:
- hacer (to do) = haría
- decir (to say) = diría
the vowel –e or –i before the –r of the infinitive is replaced by –d:
- venir (to come/arrive) = vendría
- poner (to put) - pondría
the vowel –e before the –r of the infinitive is dropped:
- saber (to know) = sabría
- poder (to be able ) = podría

1. The conditional tense tells what would refer to a particular circumstance.
- Si pasaría eso, te consigería yo los libros. (If that were to happen, I would get the books for you.)
- En ese caso, te traería tu almuerzo. (In that case, I would bring you your lunch.)
2. It expresses predictions of the past.
- Ellos estarían encantados por verlos. (I’ll bet they were thrilled to see them.)
- No habría nada que decir. (There was probably nothing to say.)
3. The verb after ”No saber si” (not to know whether) is usually in the conditional tense.
- No sabia si te importaría. (I didn’t know whether you would care.)
4. When the main verb of the sentence is in one of the past tenses, the conditional tense can describe indirect communication.
- Aviso que no llegaría. (She informed that she wouldn’t be coming.)
- Controlo que no lo botaría. (He made sure that it wouldn’t be dropped.)
5. In sentences, the conditional is used as the main clause if the si-clause (if-clause) has the verb in the imperfect subjunctive.
- Si ustedes lo dejarían, yo lo dejaría tambien. (if you all would leave it, I would leave it as well.)