La hoja del árbol cayó al suelo por el viento.

Yes, hoja has more than one meaning. It can mean:

• leaf of a tree or plant
• sheet of paper
• sometimes blade in certain contexts

In La hoja del árbol, the phrase del árbol makes it clear that hoja means leaf, because it is a leaf of the tree.

Because de + el contracts to del in Spanish.

So:

• de el árbol → del árbol

This is a standard contraction, just like:

• a + el → al

Important exception: You do not contract when el is part of a proper name, such as El Escorial.

Spanish usually uses articles more often than English.

So where English might say:

• Leaf of the tree fell...

Spanish normally prefers:

• La hoja del árbol cayó...

Here la means the, referring to a specific leaf. Without the article, the sentence would sound incomplete or unnatural in normal Spanish.

Because Spanish needs the relationship between leaf and tree to be expressed explicitly.

• la hoja = the leaf
• del árbol = of the tree

Together, la hoja del árbol means the tree’s leaf or the leaf of the tree.

You cannot normally just put two nouns together in Spanish the way English sometimes does.

Cayó is the preterite form of caer, meaning to fall.

Specifically:

• caer = to fall
• cayó = he/she/it fell

Here it refers to la hoja, which is singular, so cayó means the leaf fell.

The preterite is used because this is a completed action in the past.

Because cayó and caía express different kinds of past action.

• cayó = it fell, a completed event
• caía = it was falling / used to fall, ongoing or repeated in the past

In this sentence, the leaf fell once as a completed event, so cayó is the natural choice.

Al is the contraction of a + el.

So:

• a el suelo → al suelo

The phrase caer al suelo is very common and means to fall to the ground.

Here:

• suelo = ground, floor
• al suelo = to the ground / onto the ground

Both can relate to ground, but they are not always the same.

• suelo often means ground or floor, especially as the surface something falls onto
• tierra can mean earth, soil, or land

With falling, caer al suelo is a very common expression. It sounds natural and idiomatic.

If you said cayó a la tierra, it would sound more literary, poetic, or like you specifically mean the earth/soil.

Yes. In this sentence, por expresses cause.

So:

• por el viento = because of the wind / due to the wind

This is a very common use of por.

Other examples:

• Lo hice por ti = I did it for you / because of you
• Se canceló por la lluvia = It was canceled because of the rain

Yes, you could.

• por el viento = because of the wind
• a causa del viento = due to the wind / because of the wind

Por el viento is shorter and more everyday.
A causa del viento sounds a bit more formal or explicit.

Both cayó and se cayó are possible, but they can feel slightly different.

• cayó = fell
• se cayó = fell down

With people, se cayó is very common:

• Juan se cayó = Juan fell down

With objects, both are used, but cayó is perfectly fine here and sounds straightforward.
La hoja se cayó al suelo is also possible, though cayó may sound a bit cleaner in this sentence.

Yes, Spanish word order is somewhat flexible.

The original order is natural:

• La hoja del árbol cayó al suelo por el viento.

You could also say:

• Por el viento, la hoja del árbol cayó al suelo.

That puts more emphasis on the cause.

You might also hear:

• La hoja del árbol cayó por el viento al suelo, but that sounds less natural than the original.

So the given order is a normal, clear way to say it.

The accent marks show which syllable is stressed.

• árbol → stress on the first syllable: ÁR-bol
• cayó → stress on the last syllable: ca-YÓ

Without the accents, the stress would be read differently according to standard Spanish spelling rules.

So the accents are important for both pronunciation and correct spelling.

In Spain, hoja is pronounced roughly like OH-ha, but with a stronger throat sound for the j.

A few key points:

• h is silent
• j sounds like a strong guttural sound, similar to the ch in Scottish loch
• stress is on the first syllable: HO-ja

So it is not pronounced like English h or English j.

Most likely, yes.

The definite articles suggest something specific:

• La hoja = the leaf
• del árbol = of the tree
• el viento = the wind

In context, this usually means a particular leaf from a particular tree, and the wind as the relevant cause in that situation.

Spanish often uses the definite article where English might also use the, but sometimes Spanish uses it even where English would be less explicit.