Object pronouns

In English, the words "he" and "I" can be used as subjects (the ones doing the action in a sentence), and they change to "him" and "me" when they are objects (the ones the action is applied to). 

For example, we say "He likes me" and "I like him." "Me," "him", "her," etc. are called object pronouns.

Objects pronouns can either be direct or indirect. The direct object is the thing or person that is directly receiving the action. For example, "him" is the direct object in "she likes him." The indirect object is the receiver of the direct object. For example, "him" is the indirect object in "she writes him a book."

In English, object pronouns are the same for both direct and indirect objects, but in Spanish they can change.

The object pronouns in Spanish are:

Subject Pronoun	Direct Object Pronoun	Indirect Object Pronoun
yo	me (me/to me)
tú	te (you/to you)
él usted (masc)	lo (him, it; you)	le (to him/her/it/you)
ella usted (fem)	la (her, it; you)
nosotros/nosotras	nos (us/to us)
vosotros/vosotras	os (you/to you)
ellos ustedes (masc)	los (them; you)	les (to them/you)
ellas ustedes (fem)	las (them; you)

Unlike in English where object pronouns go after the verb ("I see him"), Spanish object pronouns are generally placed directly before the verb. Below are some examples:

English	Spanish
You write me a book	Me escribes un libro
I see you from my house	Te veo desde mi casa
I see him	Yo lo veo
I see her	Yo la veo
She writes a book to him	Ella le escribe un libro a él
He sees us	Él nos ve
I see them	Yo los veo a ellos/Yo las veo a ellas
I write them a book	Yo les escribo un libro a ellos/ellas

Further clarification about who the sentence is talking about can always be added. For example, "I see him" can be translated as "Yo lo veo" and "Yo lo veo a él." Sometimes this clarification is necessary in order to remove ambiguity, while other times it is simply redundant.

For example, "Yo los veo" is ambiguous because it could mean "I see them" or "I see you guys," so unless it is clear from context you would say "Yo los veo a ellos" or "Yo los veo a ustedes." However, "él nos ve" and "él nos ve a nosotros" mean exactly the same thing, since there is no ambiguity with "nos."