Recall that pronouns are shorter words take the place of longer nouns (people, places, things, animals, ideas, etc.). For example:
George Washington → he
the Apollo 11 moon landing → it
Goldilocks and the three bears → they
In Spanish we have many different sets of pronouns. Which set we use depends on how we're using it.
For example, there are subject pronouns:
There are object pronouns (both direct and indirect):
direct object pronouns:
indirect object pronouns:
There are reflexive pronouns:
And there are also prepositional pronouns.
While they aren't used as frequently, there is also another set of pronouns that we must use following a preposition. This kind of pronoun functions as the object of a preposition and is known as a prepositional pronoun:
Note that except for the yo and tú forms, prepositional pronouns are identical to subject pronouns. The pronoun mí carries an accent which isn't necessary for pronunciation, but helps to distinguish it from the possessive adjective, mi.
Now that we know what prepositional pronouns are, it might be a good time to review prepositions. Prepositions show a relationship between two parts of a sentence. For example:
Ella durmió en la cama.
She slept in the bed.
Ellos salieron a las cuatro.
They left at four.
El cuaderno está bajo la silla.
The notebook is under the chair.
Whenever we have a preposition followed by a pronoun, that pronoun needs to be a prepositional pronoun (not a subject pronoun). Now in most cases it won't matter if you don't know the difference, but it does matter for the yo and tú forms:
Quieren viajar con nosotros.
The want to travel with us.
Está sentada cerca de ti.
She is seated near you.
Es muy fácil para mí.
It's very easy for me.
Sí as a Prepositional Pronoun
The word sí can be used as an él/ella/Ud.- or ellos/ellas/Uds.-form prepositional pronoun. This only takes place when the subject and the object are referring to the same person or people. In this case sí means "himself," "herself," "itself," "yourself," or "themselves." For example:
Juliana compró un regalo para ella.
Juliana bought a gift for her.
Juliana compró un regalo para sí.
Juliana bought a gift for herself.
Él manda mensajes de texto a sí mismo.
He sends text messages to himself.
This use of sí is rare because reflexive verbs are typically used to convey the idea of himself/herself:
Juliana se compró un regalo.
Juliana bought herself a gift.
As usual, there are exceptions.
The preposition con merges together with the pronouns mí and ti to become conmigo and contigo. For example:
¿Quieres bailar conmigo?
Do you want to dance with me?
Necesito hablar contigo.
I need to talk with you.
When used with con, the pronoun sí becomes consigo:
Él no está contento consigo.
He isn't happy with himself.
Note: Also use a subject pronoun following hasta when it means "including."
In spite of the rules listed above, we use subject pronouns (not prepositional pronouns) after the following prepositions:
Entre tú y yo, no quiero ir.
Between you and me, I don't want to go.
Según tú, ella es experta.
According to you, she is an expert.
¡Todos estamos de acuerdo menos yo!
Everyone is in agreement except me!
Él and Ella as Prepositional Pronouns
Note: Ellos and ellas can also be used as prepositional pronouns to refer to things.
Though they are typically used as subject pronouns meaning "he" and "she," él and ella can also be used as prepositional pronouns meaning "it." For example:
El desierto es peligroso pero tengo que pasar por él.
The desert is dangerous but I need to pass through it.
A María le encanta la montaña y quiere volar sobre ella.
María loves the mountain and wants to fly over it.
In each case the pronoun agrees in gender with its antecedent: desierto → él, montaña → ella.
The Prepositional Pronoun Ello
Ello is the neuter form of the prepositional pronouns él and ella and also means "it." Ello is used when the antecedent is not a noun, but rather a gender-less concept. For example:
Llegué tarde esta mañana porque no dormí bien. No quiero hablar de ello.
I arrrived late this morning because I didn't sleep well. I don't want to talk about it.
So How Do I Say "It"?
That answer to this question depends on what part of speech "it" is. In Spanish there is no subject pronoun for "it." Simply omit the pronoun altogether if "it" is your subject:
Es muy dificil.
It is very difficult.
If "it" is a direct object, use lo or la according to the gender:
Lo compró. / La compró.
He bought it.
Lastly, if "it" is the object of a preposition, use él, ella, or ello:
¿Dónde está tu mochila? Puse mis llaves dentro de ella.
Where is your backpack? I put my keys inside it.