Te presto mi diccionario y, a cambio, tú me prestas tu cuaderno.

Because prestar usually needs an indirect object: the person who receives the thing being lent.

• Te presto mi diccionario = I lend my dictionary to you
  • te = to you
• Tú me prestas tu cuaderno = you lend your notebook to me
  • me = to me

So:

• te = the receiver is you
• me = the receiver is me

This is very common in Spanish with verbs like dar, decir, mandar, prestar, etc.

Spanish normally uses the indirect object pronoun (me, te, le, nos, os, les) rather than the full phrase with a.

So the natural version is:

• Te presto mi diccionario

You can add a ti for emphasis or contrast:

• Te presto mi diccionario a ti, no a él.

But on its own, te presto is the normal everyday wording.

Yes, subject pronouns are often optional in Spanish because the verb ending already shows who the subject is.

• me prestas already means you lend me

So why say tú here?

Because it adds contrast or emphasis:

• I lend you my dictionary and, in return, you lend me your notebook.

The sentence sets up a kind of exchange, so tú helps highlight that the other person is expected to do their part.

Without tú, the sentence is still correct:

• Te presto mi diccionario y, a cambio, me prestas tu cuaderno.

That sounds natural too, just a little less emphatic.

A cambio means in exchange or in return.

In this sentence:

• y, a cambio, tú me prestas tu cuaderno
• = and, in return, you lend me your notebook

It introduces the idea of a reciprocal arrangement: one thing is given in exchange for another.

A very common longer form is:

• a cambio de = in exchange for

For example:

• Te doy esto a cambio de eso.
• I give you this in exchange for that.

But here, a cambio by itself works because the exchange is already clear from the context.

Yes, in many situations prestar and dejar can both mean to lend.

• Te presto mi diccionario
• Te dejo mi diccionario

Both can mean I lend you my dictionary.

However, prestar is the most direct equivalent of to lend, while dejar has other meanings too, especially to leave or to let.

For learners, it is often easier to understand this sentence with prestar because it clearly focuses on lending.

In Spain, both verbs are common, depending on context.

Because mi and tu are the short possessive adjectives used before a noun:

• mi diccionario = my dictionary
• tu cuaderno = your notebook

By contrast, mío and tuyo are usually used after a noun or as pronouns:

• Este diccionario es mío. = This dictionary is mine.
• Tu cuaderno y el mío = Your notebook and mine

So before a noun, Spanish normally uses:

• mi, tu, su, nuestro, etc.

Not:

• mío diccionario ❌
• tuyo cuaderno ❌

Because Spanish usually does not use an article when a possessive adjective is already there.

So you say:

• mi diccionario
• tu cuaderno

not:

• el mi diccionario ❌
• el tu cuaderno ❌

The possessive already identifies the noun, so no article is needed.

Spanish often uses the present tense to talk about a near future or an arranged action, just like English sometimes does.

So:

• Te presto mi diccionario y, a cambio, tú me prestas tu cuaderno

can sound like:

• I’ll lend you my dictionary and, in return, you lend me your notebook

The present tense here makes the exchange sound immediate, natural, and conversational.

If you wanted, you could also make it more explicitly future:

• Te prestaré mi diccionario y, a cambio, tú me prestarás tu cuaderno.

But that can sound more formal or more deliberate.

The structure is:

• Te = indirect object pronoun = to you
• presto = I lend
• mi diccionario = direct object = my dictionary

So the pattern is:

indirect object pronoun + verb + thing

This is very common in Spanish:

• Te doy un libro. = I give you a book.
• Le mando un mensaje. = I send him/her a message.
• Nos prestan dinero. = They lend us money.

English often puts the receiver after the verb with to, but Spanish often uses the pronoun before the verb.

Because a cambio is being used like an inserted expression, similar to in return in English.

So the commas help mark that parenthetical pause:

• Te presto mi diccionario y, a cambio, tú me prestas tu cuaderno.

Without commas, people would still understand it, but with commas it is clearer and more natural in writing.

It reflects the rhythm:

• I lend you my dictionary and, in return, you lend me your notebook.

It would be understood perfectly across the Spanish-speaking world. Nothing in it is uniquely Spanish from Spain.

However, it fits Spain Spanish naturally because:

• tú is the normal informal singular you in Spain
• cuaderno and diccionario are completely standard everywhere
• prestar is universally understood

If the sentence were aimed at a formal situation, you might use usted instead:

• Le presto mi diccionario y, a cambio, usted me presta su cuaderno.

But the original sentence is a normal informal version.

Yes, Spanish allows some flexibility, but some versions sound more natural than others.

Original:

• Te presto mi diccionario y, a cambio, tú me prestas tu cuaderno.

Possible variation:

• Yo te presto mi diccionario y tú, a cambio, me prestas tu cuaderno.

Still correct:

• Te presto mi diccionario y tú me prestas tu cuaderno a cambio.

But that last one can sound slightly less elegant, because a cambio fits very naturally as an inserted phrase in the middle.

So the original version is a very good, natural choice.

You would change the pronouns and possessives to match usted:

• Le presto mi diccionario y, a cambio, usted me presta su cuaderno.

Changes:

• te → le = to you (formal)
• tú → usted
• tu cuaderno → su cuaderno

This is the polite singular form used with someone you would address as usted.