Learn Italian: Siamo rimasti in città.

In Italian, the past tense is usually formed with avere (to have). However, verbs that describe movement or a state of being, like rimanere (to stay/remain), use essere (to be) as their helper verb. That is why we say siamo rimasti (literally 'we are stayed').

Why does the past participle rimasti end in -i?

When a past tense verb uses essere as its helper verb, the past participle acts like an adjective and has to match the subject. Because the subject 'we' is plural, the ending changes to the masculine plural -i. If the group consisted entirely of women, it would be siamo rimaste.

What verb does rimasti come from? It does not look like a regular past tense ending.

It comes from the verb rimanere (to stay or remain). It is an irregular verb, which means its past participle does not follow the normal pattern. Instead of a predictable ending, it changes to rimasto (and here, the plural rimasti).

Why is it just in città and not nella città (in the city)?