El cachorro muerde su juguete.

In Spanish, singular countable nouns usually need a determiner like el, un, mi, este, etc.

So Spanish normally says:

• el cachorro = the puppy
• un cachorro = a puppy

You generally would not say just cachorro muerde... in a normal sentence.

Here, el is the masculine singular definite article because cachorro is masculine singular.

Morder is the infinitive, meaning to bite.
In a full sentence, you usually need a conjugated verb.

Muerde is the third-person singular present tense form of morder:

• yo muerdo
• tú muerdes
• él/ella/usted muerde

Since el cachorro is a third-person singular subject, muerde is the correct form.

Because morder is a stem-changing verb in the present tense. Its o changes to ue in most present-tense forms.

So:

• morder
• yo muerdo
• tú muerdes
• él/ella/usted muerde

But not:

• nosotros mordemos
• vosotros mordéis

This kind of change is very common in Spanish.

Su is a possessive adjective. It can mean:

• his
• her
• its
• your (formal)
• their

So su juguete could mean his toy, her toy, its toy, your toy (formal), or their toy, depending on context.

In this sentence, context usually makes it clear that it means the puppy’s toy, so in English that would often be its toy.

They can add extra clarification if needed:

• su juguete = his/her/its/their toy
• el juguete del cachorro = the puppy’s toy
• su juguete de él = his toy
• su juguete de ella = her toy

In everyday Spanish, people usually rely on context first. If context is not enough, they make it more explicit.

In Spanish, possessive adjectives like mi, tu, su, nuestro usually replace the article.

So you say:

• su juguete
• not el su juguete

This is similar to English:

• his toy
• not the his toy

Not all Spanish nouns follow the -o = masculine, -a = feminine pattern. Nouns ending in -e can be either masculine or feminine.

Juguete happens to be masculine, so it takes:

• el juguete
• un juguete

You usually have to learn the gender together with the noun.

Yes. Spanish often drops subject pronouns, and sometimes even noun subjects if they are already understood from context.

So depending on context, you might hear:

• Muerde su juguete.

This can still be a complete sentence if it is clear who is biting the toy.

But with el cachorro included, the sentence is more explicit.

The simple present in Spanish is very flexible. It can describe:

• a general action
• a habitual action
• something happening right now, depending on context

So muerde can work for bites or even is biting in the right situation.

If you want to strongly emphasize that the action is in progress right now, Spanish can also use:

• El cachorro está mordiendo su juguete.

Both are possible, but muerde is completely natural.

In Latin American Spanish, cachorro is roughly pronounced:

ka-CHO-rro

A few key points:

• ch sounds like English ch in chair
• the rr is a strong rolled or trilled r
• the stress falls on cho: ca-CHO-rro

The rr is different from a single r in Spanish. It is stronger and longer.

Not always. Cachorro can mean a young animal in general, depending on context. In everyday use, though, it very often means puppy.

So learners will commonly see:

• cachorro = puppy

But in other contexts, it can also refer to a cub or young animal.

Yes, Spanish word order is more flexible than English, though El cachorro muerde su juguete is the most neutral and natural order.

This basic order is:

• subject + verb + object

Spanish can change the order for emphasis, style, or context, but for learners, this standard pattern is the best one to use first.