Learn Hardcore Italian: Soltanto il vento muove le foglie in giardino. - Only the wind moves the leaves in the garden.

Soltanto and solo are both adverbs meaning “only.” In this sentence you could swap them:
• Solo il vento muove le foglie in giardino sounds perfectly natural.
Soltanto tends to be a bit more formal or emphatic. Also, solo can function as an adjective (“lui è solo”), whereas soltanto is strictly an adverb.

Does soltanto modify il vento or muove? In other words, does it mean “only the wind moves…” or “the wind only moves…”?

Word order signals what is restricted:
• Soltanto il vento muove… restricts the subject: “only the wind” (no other force).
• Il vento muove soltanto le foglie… restricts the object: “only the leaves” (nothing else is moved).
• Il vento muove le foglie soltanto in giardino restricts the location: “only in the garden.”

Why is there a definite article (il) before vento? In English we say just “wind.”

Italian usually uses the definite article with generic nouns. To talk about wind in general, you say il vento. Omitting the article (vento muove…) would sound incorrect.

Similarly, why do we say le foglie instead of just foglie?

For the same reason: generic or plural nouns in Italian take the definite article. Le foglie means “the leaves” in general. Without le, it would sound like you’re listing or speaking of leaves in an indefinite sense.

Why is the verb muove in third-person singular instead of third-person plural (muovono)?

The verb agrees with its subject. Here the subject is il vento (singular), so the form is muove. If the subject were plural—e.g. le correnti—you would say le correnti muovono.

Why is it in giardino without any article, rather than nel giardino or nella giardino?

Both in giardino and nel giardino are grammatically correct, but:
• In giardino (no article) is the idiomatic way to indicate being in a garden in general.
• Nel giardino (in + il) emphasizes “inside the boundaries of the garden.”
You never say nella giardino because giardino is masculine (it would be nel).

Can I move soltanto to other positions in the sentence?

Yes. Changing its position shifts the focus:
• Il vento muove soltanto le foglie in giardino. (“only the leaves”)
• Il vento soltanto muove le foglie in giardino. (emphatic, less common – “nothing but the wind moves them”)
Italian word order is flexible, but listen for how the emphasis changes.

Could I replace muove with another verb like sposta?

You could, but spostare has a nuance of carrying or relocating something to a different spot.
• Il vento sposta le foglie implies the wind is piling or shifting leaves around.
• Muovere is more general – it just indicates motion.

Is there a passive version of this sentence in Italian?

Yes. You can say:
Le foglie in giardino sono mosse soltanto dal vento.
Here you use the past participle mosse (agrees with le foglie) and introduce the agent with da.