This question has never really come up in my Spanish classroom...
...unless my memory deceives me!
I have taught Spanish for a good while (my grey hair bears witness to that!) but it has never really come up.
.... in a classroom situation you can get stuck into the "weeds" of on particular type of infinitive and do not take a 360 degree overview.
And, the purpose of this article is to take a 360 degree overview.
Once that has been done, you will find out where the different infinitive forms came from.
What is an infinitive?
It may be worthwhile just setting down a clear definition of an infinitiveThe infinitive of a verb is the basic form, for example 'do', 'be', 'take', and 'eat'. The infinitive is often used with 'to' in front of it.
Source : COBUILD Advanced English Dictionary. Copyright © HarperCollins Publishers
How many types of infinitives are there in Spanish?
The short answer is three.
... but look under the surprise section below!
The first infinitive type is the -ar form.
Here are some common regular -ar verbs:
pasar - to pass, spend time
quedar - to remain, stay
hablar - to speak
The regular -ar verbs, as their name implies, follow a regular pattern in their formation.
Here are some common irregular -ar verbs:
estar - to be
dar - to give
andar - to walk
The irregular -ar verbs, as their name implies, are sometimes irregular in their formation. They do not follow the rules!
The first infinitive type is the -er form.
Here are some common regular -er verbs:
beber - to drink
comer - to eat
meter - to put
The regular -er verbs, as their name implies, follow a regular pattern in their formation.
Here are some common irregular -er verbs:
haber - to have (the grammatical "have")
tener - to have (i.e. possession)
saber - to know (a fact)
The irregular -er verbs, as their name implies, are sometimes irregular in their formation. They do not follow the rules!
The first infinitive type is the -ir form.
Here are some common -ir verbs:
vivir - to live
existir - to exist
ocurrir - to occur
The regular -ir verbs, as their name implies, follow a regular pattern in their formation.
Here are some common irregular -ir verbs:
decir - to say , to tell
venir - to come
salir - to go out
The irregular -ir verbs, as their name implies, are sometimes irregular in their formation. They do not follow the rules!
Why do these different Spanish infinitive forms exist?
Spanish is derived from Latin.
Early ancient Roman grammarians originally divided the Latin verb system into three conjugation types.
However, later grammarians recognised four.
The following table gives an idea of how verbs made the transition form Latin into Spanish.
The four Latin conjuGation (infinitive) types
(1) amō, amāre "to love" - this has become amar in Spanish
(2) videō, vidēre "to see" - this has become ver in Spanish
(3) regō, regere "to rule" - this has become reinar in Spanish
(4) audiō, audīre "to hear" - - this has become oir in Spanish
A surprise! -ÍR
If you really wanted to be "picky", and academic grammarians in their nature fit into this category, there is actually a fourth infinitive ending.
... but it might be pushing a point!
However, here I go....
...some Spanish verbs end in ír (and not plain old -ir).
Well, this level of detail is not for everyone, but (depending on my mood - especially if I am an exam marking mode!) I confess to liking this!
Here are the verbs in all their glory!
to grow conceited
This has been a brief overview and an attempt to answer the question - how many types of infinitives are there in Spanish?
Well - perhaps you were expecting the answer to be 3.
... and you are right!
But, there was a slight twist in the story...
It could be argued that there are, in fact, 4.
And the argument that there are, in fact, is a pedant's delight!
... but life is too short!