Learn Polish: Lewy dom jest stary. - The left house is old.

They are both adjectives describing the masculine noun dom (house). In Polish, adjectives describing a masculine noun in the subject form (the nominative case) usually end in -y.

Why do we use jest instead of to in this sentence?

We use jest because the sentence links a noun (dom) to an adjective (stary). You generally use the word to instead when you are linking a noun to another noun, such as saying 'A house is a building'.

Is the word order strictly adjective before noun here? Could I say dom lewy?

For regular descriptive adjectives like lewy, you put them before the noun, exactly like in English. So lewy dom is the natural word order. Putting the adjective after the noun is mostly used for official categories, like in biology or official names.

Would the words lewy and stary change if we were talking about a feminine word?

Yes! Polish adjectives must match the gender of the noun they describe. If you were talking about a feminine noun like ulica (street), both adjectives would take the feminine -a ending instead, making it Lewa ulica jest stara.