This rule was helpful
I got the book "English Grammar for Students of Spanish" on the recommendation of someone on DuoLingo. It's been invaluable. Like others, the first lesson in this series was very frustrating for me, so I decided to consult the book to see what they said on infinitive use.
"In a sentence the infinitive form is always used for a verb that follows any verb other than ser, estar, or haber. For example:
John and Mary want to dance together. Juan y María quieren bailar juntos.
I can leave tomorrow. Puedo salir mañana.
You should study more. Usted debe estudiar más.
Notice that in the last two examples there is no "to" in the English sentence to alert you that an infinitive must be used in Spanish."
Whew! Now I feel like I get it (mostly).
There is also:
- To know how to do something = saber +inf (I know how to cook = sé cocinar).
- To need to do something = necesitar + inf (I need to run = necesito correr)
Some verbs insert either an "a" or a "de" between the two verbs.
- I have to do something = Tener que + inf (I have to cook = Tengo que cocinar).
- I learn to do something = Aprender a + inf (I learn to cook = Aprendo a cocinar).
- I try to do something = Tratar de + inf (I try to be happy = Trato de ser feliz).
- To have just finished something = Acabar de + inf (I just finished cooking = Acabo de cocinar).
- To start doing something = Empezar/Comenzar a + inf (I start dancing = Empezo a bailar).
Is there a rule to know when to insert an "a", "que" or "de" before these verbs, or is it completely arbitrary and needs to be learnt through practice?
I think you need to just memorize it, that's what I did :S.
You can google it, there are a ton more verbs, I only listed ones I've actually been using.
Actually, I saw in the "gerund" section someone had posted this list: http://spanishplus.tripod.com/VerbsandPrepositions.htm#TopOfPage
Knock yourself out :)
Woah, that's an exhaustive list! It's definitely going to take a while.
¡Muchas gracias por el link!
I've always thought of infinitives as referring to the core idea of the verb, with no subject. So, in "John and Mary want to dance together", "to dance" is the core idea of dancing. It's nearly a noun. So, the infinitive is used. Likewise, in "You should study more", "study" has no subject. It only refers to the idea of studying. It's almost like an object of the auxiliary verb "should".
Another helpful way of thinking about it might be this:
If there is no "-s" ending in the english sentence while using it for a third person singular subject, it shows that you are, even in english, actually using an infinitive form of the verb.
I can leave tomorrow. => He can leave tomorrow. (Not: He can leaves tomorrow) You should study more. => He should study more. (Not: He should studies more)