Ellos guardan sus libros en la mochila.

They keep their books in the backpack.

Breakdown of Ellos guardan sus libros en la mochila.

• el libro: the book
• en: in
• ellos: they
• la mochila: the backpack
• guardar: to keep
• sus: their

Questions & Answers about Ellos guardan sus libros en la mochila.

Why is the word ellos used here? Could you also say Guardan sus libros en la mochila without ellos?

In Spanish, the subject pronoun (like yo, tú, él, ellos) is usually optional, because the verb ending already shows who is doing the action.

• Ellos guardan sus libros en la mochila
• Guardan sus libros en la mochila

Both are grammatically correct and mean the same thing in most contexts.

You include ellos when:

• You want to emphasize who is doing the action (e.g., They do it, not someone else).
• You want to avoid ambiguity (for example after talking about several possible subjects).

If the context is clear, native speakers often drop ellos and simply say Guardan sus libros en la mochila.

Why is the verb guardan and not guardar or guarda?

Guardar is the infinitive form (to put away / to keep / to store).

In this sentence, we need the present tense form that matches ellos (they).
The present tense forms of guardar are:

• yo guardo
• tú guardas
• él / ella / usted guarda
• nosotros guardamos
• ellos / ellas / ustedes guardan

Since the subject is ellos, the correct form is guardan.
Guardar alone would be like saying to keep instead of they keep.

Does guardar just mean to guard, like in English? What exactly does it mean here?

In Spanish, guardar is broader than English to guard. Common meanings include:

• to put away / to put back:
  
  • Ellos guardan sus libros en la mochila. → They put their books away in the backpack.
• to keep / to save:
  
  • Guarda los recibos. → Keep/save the receipts.
• to store:
  
  • Guardamos la ropa de invierno en cajas. → We store our winter clothes in boxes.

In this sentence, the meaning is to put away / put back / keep the books in the backpack, not to protect them like a guard.

Why is it sus libros and not su libros?

The possessive adjective (su / sus) must agree in number with the noun, not with the owner.

• su libro → his book / her book / their book / your (formal) book
• sus libros → his books / her books / their books / your (formal) books

Here, libros is plural, so the possessive must also be plural: sus libros.

It is not plural because of ellos, but because of libros.

Can sus here also mean his books or her books, not just their books?

Yes. Sus is ambiguous without context. It can mean:

• his books
• her books
• their books
• your books (formal, talking to usted or ustedes)

In this sentence, ellos tells us we are talking about they, so we understand sus as their.

If you need to be very clear, you can use de:

• los libros de él → his books
• los libros de ella → her books
• los libros de ellos → their books (belonging to them)
• sus libros → could be any of the above, depending on context

Why is there no article like los before libros? Why not Ellos guardan los libros en la mochila?

In Spanish, when you use a possessive adjective (mi, tu, su, nuestro, su etc.), you do not also use a definite article (el, la, los, las) before the noun:

• mis libros, not los mis libros
• tus cuadernos, not los tus cuadernos
• sus libros, not los sus libros

So sus libros already includes the idea of the and their together: their books.

Why is it la mochila and not el mochila? How do I know mochila is feminine?

Every Spanish noun has a grammatical gender: masculine or feminine.
Mochila (backpack) is feminine, so it takes the feminine article la:

• la mochila → the backpack

A general pattern (with many exceptions) is:

• Nouns ending in -a are often feminine: la mochila, la casa, la mesa
• Nouns ending in -o are often masculine: el libro, el cuaderno, el vaso

You mainly learn the gender of each noun with practice, but mochila is always feminine: la mochila / las mochilas.

Why is it la mochila (singular) and not sus mochilas (their backpacks)?

Both are possible, but they describe different situations:

• Ellos guardan sus libros en la mochila.
  Suggests they put their books into one backpack (maybe a shared bag or we’re just focusing on a single bag).

• Ellos guardan sus libros en sus mochilas.
  Suggests each person has their own backpack, and they each put their books into their own bag.

The sentence with la mochila doesn’t say how many backpacks exist in total, only that the books go in the backpack being referred to.

Why is the preposition en used? Is it in or into?

Spanish en covers both in and on, and, in many cases, the English idea of into when the result is a location.

Here:

• guardan sus libros en la mochila
  = they put their books in / into the backpack.

If you want to be very explicit, you could use dentro de (inside of):

• Ellos guardan sus libros dentro de la mochila.
  → They keep their books inside the backpack.

But en la mochila is the normal, natural way to say it.

What’s the difference between ellos and ellas?

Both mean they, but they differ in gender:

• ellos = they (all males) or a mixed group (males and females)
• ellas = they (all females)

So:

• Ellos guardan sus libros en la mochila. → a group of all men, or men + women.
• Ellas guardan sus libros en la mochila. → a group of only women/girls.

In mixed groups, ellos is the default in standard Spanish.

How do you pronounce the ll in ellos? And how is guardan pronounced?

Pronunciation varies by region in Latin America, but common patterns are:

• ellos

  • In most of Latin America, ll sounds like the English y in yes:
    [EH-yos] or [EH-jos] (depending on accent).
  • In places with yeísmo rehilado (e.g., Argentina), it can sound like the s in measure or like sh: [EH-shos] or [EH-zhos].

• guardan

  • The gua is like gwa in Guatemala: [GWA]
  • The r is a single tap [ɾ] (a quick flap, like the t in American water).
  • Final -n is clearly pronounced.
    Approximate: [GWAɾ-dan].

Can the word order change? For example, can I say Ellos sus libros guardan en la mochila?

Spanish word order is generally Subject – Verb – (Objects), especially in neutral, everyday sentences:

• Ellos guardan sus libros en la mochila.

You can change the order in some cases for emphasis or style, but not all orders sound natural. For this sentence:

• Ellos guardan sus libros en la mochila. → Totally natural.
• Guardan ellos sus libros en la mochila. → Possible, but sounds more emphatic or poetic.
• Ellos sus libros guardan en la mochila. → Sounds strange or incorrect in normal speech.

For now, as a learner, it’s safest to keep the normal order: [Subject] + [Verb] + [Object/Complement] → Ellos guardan sus libros en la mochila.

In English we might say They are putting away their books. Why does Spanish use a simple present (guardan) and not están guardando?

Spanish simple present (guardan) is used more widely than English simple present:

• Ellos guardan sus libros en la mochila.
  Can mean:
  • They put away their books (habitually, every day), or
  • They are (now) putting away their books, depending on context.

If you really want to emphasize that the action is happening right now, you can use the progressive:

• Ellos están guardando sus libros en la mochila. → They are putting away their books (right now).

Both are correct; the simple present is more common and more flexible.