El hombre abre la ventana porque tiene calor.

In Spanish, singular countable nouns usually need an article or another determiner. So el hombre means the man.

Saying just hombre by itself would usually sound incomplete in a normal sentence like this. Spanish uses articles more often than English does.

Because Spanish nouns have grammatical gender.

• hombre is masculine, so it takes el
• ventana is feminine, so it takes la

These articles agree with the noun:

• el hombre
• la ventana

This is grammatical gender, not biological sex in every case. For hombre, the natural and grammatical gender both happen to be masculine.

Abre is the present tense, third person singular, of the verb abrir (to open).

So:

• yo abro = I open
• tú abres = you open
• él / ella / usted abre = he / she / you open

In this sentence, abre means opens or sometimes is opening, depending on context.

Spanish often leaves out subject pronouns when they are not needed. This is because the verb form already shows who the subject is.

Here, tiene means he/she/it has, and from context we understand it refers to el hombre.

So Spanish naturally says:

• El hombre abre la ventana porque tiene calor.

Instead of repeating:

• El hombre abre la ventana porque él tiene calor.

Adding él is possible, but usually only for emphasis or contrast.

It refers to the man.

Grammatically, Spanish often keeps the same subject unless something signals a change. Here the most natural reading is:

• The man opens the window because he is hot

not

• The man opens the window because the window is hot

Also, tener calor is an expression used for people and animals feeling hot, so that strongly points to el hombre.

Because Spanish uses the idiom tener calor, literally to have heat, to mean to feel hot.

So:

• Tengo calor = I’m hot
• Tienes calor = You’re hot
• Tiene calor = He/She is hot

This is one of those places where Spanish and English use different structures. A native English speaker may want to say está caliente, but that usually means something itself is physically hot to the touch, not that a person feels hot.

They are very different.

• tener calor = to feel hot
• estar caliente = to be hot, heated, warm/hot physically

Examples:

• Tengo calor = I feel hot
• La sopa está caliente = The soup is hot

For a person, estar caliente can sound odd or mean something very different depending on context, so learners should use tener calor when talking about feeling hot.

Because porque is the conjunction meaning because.

Spanish distinguishes several similar forms:

• porque = because
• por qué = why
• el porqué = the reason
• por que = less common combination in certain structures

In your sentence, it introduces the reason, so porque is correct:

• abre la ventana porque tiene calor = he opens the window because he is hot

Because la ventana is a direct object, and it is an inanimate thing.

Spanish uses the personal a mainly before specific human direct objects, and sometimes pets or personified beings. For example:

• Veo al hombre = I see the man

But with things:

• Abre la ventana = He opens the window

So no a is needed here.

Because abre is acting on la ventana as a direct object.

• El hombre abre la ventana = The man opens the window

Here:

• el hombre = subject
• abre = verb
• la ventana = object

If you said la ventana abre, that would mean the window opens, where la ventana becomes the subject. That changes the meaning.

Yes. That means The man is opening the window because he is hot.

The difference is:

• abre = simple present; can mean opens or sometimes is opening
• está abriendo = explicitly emphasizes the action is in progress right now

Both are correct, but abre is the simpler, more neutral form.

In standard Spanish, h is silent.

So hombre is pronounced roughly like OMBRE.

This is true in words like:

• hola
• hacer
• hombre

A native English speaker often expects the h sound, but in Spanish it normally disappears.

Yes, that is grammatically correct.

It means the same thing, but it changes the emphasis slightly by putting the reason first:

• Porque tiene calor, el hombre abre la ventana.
• El hombre abre la ventana porque tiene calor.

The second version is more neutral and probably more common in basic examples, but both are fine.

Here la ventana means the window, so the sentence is talking about a specific window.

Spanish often uses definite articles in places where English might choose differently depending on context, but in this sentence the window is the natural translation.

If you wanted a window, you would normally say:

• una ventana

So:

• abre la ventana = opens the window
• abre una ventana = opens a window

Yes. Calor is a noun meaning heat.

In the expression tener calor, Spanish uses the verb tener (to have) plus the noun calor to express the idea of feeling hot.

So literally:

• tiene calor = he has heat

But naturally in English:

• he is hot
• he feels hot