Learn Russian: У нас есть интересная идея.

In Russian, you don't typically use a direct verb for 'to have'. Instead, you use a structure that literally means 'by us exists'. У means 'by', нас is 'us', and есть means 'is' or 'exists'.

Where does the word нас come from?

Нас is the genitive case form of мы (we). The preposition у always requires the pronoun that follows it to be in the genitive case, so мы changes to нас.

If 'we' is нас, what is the actual subject of this sentence?

The grammatical subject is actually интересная идея (an interesting idea). Because the sentence literally translates to 'By us exists an interesting idea,' the idea is the thing doing the existing. That is why it stays in the nominative (dictionary) case.

Why is the adjective интересная instead of the dictionary form интересный?

Adjectives must match the gender of the noun they describe. Идея ends in -я, making it a feminine noun. Therefore, the adjective takes the feminine ending -ая, becoming интересная.