Learn Italian: Ha pulito la stanza senza spostare i mobili. - He cleaned the room without moving the furniture.

When the subject of the main action (he cleaned) and the excluded action (he didn't move) are the same person, Italian uses senza followed directly by the infinitive. While English uses 'without' + an '-ing' verb, Italian requires the infinitive for this structure.

Why do we use the present infinitive spostare if the main action (ha pulito) happened in the past?

We use the present infinitive because the two actions happened at the same time. The fact that he didn't move the furniture was simultaneous with him cleaning the room. You only use the past infinitive, like senza avere spostato, if the excluded action happened before the main one.

If I wanted to say 'He cleaned the room without ME moving the furniture,' would I still use senza spostare?

No. You can only use the implicit senza + infinitive structure when the subject of both actions is the exact same person. If the subjects are different, you have to use an explicit clause with senza che followed by the subjunctive mood.

Why is i mobili plural in Italian but translated as the singular 'furniture' in English?

In English, 'furniture' is an uncountable noun and always singular. In Italian, il mobile refers to a single piece of furniture, so it is countable. To talk about multiple pieces or furniture in general, you use the plural form i mobili.