The future tense is one of the two tenses (the other being the conditional tense) used to describe upcoming events or situations. They are the only two simple tenses in Spanish that are not formed from the stem, but from the infinitive. The future tense is used to say what will happen. It is formed by adding a special set of endings to the infinitive of all verbs.

Note:
A.There are many common verbs that use a modified form of the future tense. The endings are stll the same though.
reduced infinitives:
- hacer (to do) = haré
- decir (to say) = diré
the vowel –e or –i before the –r of the infinitive is replaced by –d:
- venir (to come/arrive) = vendré
- poner (to put) - pondré
the vowel –e before the –r of the infinitive is dropped:
- saber (to know) = sabré
- poder (to be able ) = podré
B. The future of the verb hay (there is) is habrá

1. The future tense refers to future time.
- Mi amiga viajará mañana. (My friend will travel tomorrow)
Often, in speech the future tense is expressed by replacing the future tense form with the word ir or a plus the infinitive form of the verb. - Mi amiga va a viajar mañana. (My friend is going to travel tomorrow)
It can also be replaced by the simple present form if the sentence makes it clear that the future is being referred to.
- Mi amiga viaja mañana. (My friend travels tomorrow)
2. The Future tense is commonly used to refer to the present as well. It is expressed more as speculation or wonder about things occurring in the present.
- Donde estará mi madre? (Where can my mother be?)
- Quien tendrá su numero? (Who can happen to have his number?)
3. It can also be used to speculate or mention things that are probably happening in the present time.
- Tu tío sabrá donde esta la tienda. (I Guess your uncle will know where the store is.)
- Habrá mucha gente. (There must be many people.)
4. “No saber si” (not to know whether) is commonly used in spanish and it is expressed in the future tense.
- No se si podré ir a tu casa. (I don’t know whether I’ll be able to go to your house.)
5. The future tense is also used to describe indirect communication when the main verb of the sentence is in present tense.
- Dice que podrá traer tu mochila. (He/She says he will be able to bring your backpack.)
- Escribe que no tendrá tiempo. (He/She writes that he will not have time.)
6. In sentences with if-clauses, or si-clause, it is used as the main clause if the verb is in present tense.
- Si ellos viajan, yo viajaré tambien. (If they travel, then I will travel as well.)
(Yo viajaré tambien, si ellos viajan.)