Conditional Tense

The conditional tense is used to express the idea that something would happen with the implication that its happening depends on some other condition. Often times this other condition is expressed in a si clause which is usually in the imperfect subjunctive. Other times it appears with a pero clause. And finally, the conditional is used to express a future action in a subordinate (que) clause when the action of the main verb is in the past.

Yo jugaría con Uds. en el partido si no estuviera herido. I would play with you all in the game if I wasn't hurt.
Me gustaría ir a tomar un café contigo, pero tengo que estudiar. I would like to go drink a coffee with you, but I have to study.
Sabíamos que te cambiarías de opinión. We knew that you would change your opinion.

The conditional tense is formed by adding –ía, -ías, -ía, -íamos, -íais, or –ían to the end of the infinitive form of the verb.

hablar hablaría, hablarías, hablaría, hablaríamos, hablaríais, hablarían
comer comería, comerías, comerías, comeríamos, comeríais, comerían
vivir viviría, vivirías, viviría, viviríamos, viviríais, vivirían

Verbs that have irregular forms in the future are also irregular in the conditional. They use the same stem in the conditional as they did in the future tense.

decir: dir-
hacer: har-
poder: podr-
poner: pondr-
querer: querr-
saber: sabr-
tener: tendr-
venir: vendr-