Learn Polish: Zostaw płaszcz w szatni podczas spektaklu. - Leave your coat in the cloakroom during the performance.

It uses the suffix -nia, which is one of the most common ways to form a place noun. It attaches to the root word szata (an old word for a robe or garment). Together, they literally mean a garment room, which is how we get the word for cloakroom. You have likely seen this same suffix in other places, like piekarnia (bakery) or kawiarnia (cafe).

Why does the locative form of szatnia end in -ni (w szatni) rather than the typical feminine -e?

Feminine nouns that end in a soft consonant plus -a (like -nia, -cia, or -sia) take an -i ending in the locative case instead of -e. Because szatnia has that soft -ni- sound, it becomes szatni. The -e ending is reserved for feminine nouns that end in a hard consonant before the final -a.

Why is the word for performance in the form spektaklu here?

The preposition podczas (during) always requires the noun that follows it to be in the genitive case. Since spektakl is a masculine inanimate noun, it takes the standard genitive ending -u, giving us spektaklu.

Why use the perfective imperative instead of the imperfective ?