Learn Hardcore Russian: Я записал адрес библиотеки.

Записал is the past tense, perfective aspect of записать, which means “to write down” or “to record.” The perfective aspect signals that the action is viewed as completed. If you wanted to describe a past, ongoing or habitual action without emphasizing its completion, you would use the imperfective записывал.

What case is адрес, and why does it look the same as the nominative?

In this sentence адрес is in the accusative case because it’s the direct object of записал. Inanimate masculine nouns have identical forms for nominative and accusative singular, so адрес doesn’t change its ending.

Why is библиотеки in the genitive case?

Russian expresses “of …” or possession by putting the noun in the genitive. Адрес библиотеки literally means “address of the library.” Therefore библиотеки is the genitive singular of библиотека.

How would I say “I write down the library’s address” in the present tense?

Use the imperfective present tense: Я записываю адрес библиотеки. Here записываю is the 1 st person singular present tense of записывать, indicating an ongoing or habitual action.