For example, why is the "a" needed in "vamos a comer"? Why isn't it just "vamos comer"?
1Hello, Caleb, welcome to this site. You should check the related questions that appear in the right column. There is one answered by Charlie that is not an exact duplicate of yours but almost: spanish.stackexchange.com/questions/30631/…– RubioRicSep 22, 2020 at 14:05
The periphrastic future is formed by "ir + a + infinitive", so "vamos comer" is not grammatical. You need to say: "Vamos a comer".
Most verbs that are followed by an infinitive will not take "a":
- Quiero comer (I want to eat).
- Prefiero comer (I prefer to eat).
- Deseo comer (I wish to eat).
- Pienso / Planeo comer (I intend/plan to eat).
- Decido comer (I decide to eat).
- Necesito comer (I need to eat).
- Prometo comer (I promise to eat).
- Intento comer (I try to eat).
Sometimes, "a" is used:
- Empiezo / Comienzo a comer (I begin/start eating/to eat).
- Me rehúso/resisto a comer (I refuse to eat).
- Vuelvo a comer (I eat again, I resume eating).
Sometimes, other prepositions like "de" or "en" are used:
- Termino de comer (I finish eating).
- Dejo de comer (I stop eating).
- Trato de comer (I try to eat).
- Pienso en comer (I think of eating).
Sometimes, "que" is used:
- Tengo que comer (I have to eat).
Therefore, the main verb (the one that precedes the infinitive) will define if any word will be inserted in between.
The preposition "a" will always be used if it precedes an infinitive of purpose:
- Vengo a comer (I come to eat = I come in order to eat).
- Salgo a comer (I go out to eat = I go out in order to eat).
"Rehúso comer" se usa en el español europeo.– wimi ♦Sep 22, 2020 at 14:46
@wimi Gracias por el dato. Aquí usamos ambas formas: me rehúso a comer o rehúso comer. Sep 22, 2020 at 15:03