Questions & Answers about Ulica jest mokra po deszczu.
Why does the adjective mokra end in -a?
It describes the noun ulica (street), which is feminine. Adjectives must match the gender of the noun they describe, so the dictionary form mokry changes to the feminine form mokra.
Why is the word for rain deszczu here instead of just deszcz?
The preposition po, when used to mean 'after' an event or time, requires the following noun to be in the Locative case. So the base word deszcz changes to its Locative form, deszczu.
Doesn't the Locative case usually add -e to masculine nouns? Why does deszcz take -u?
While many masculine nouns do take -e, nouns ending in a 'hardened' consonant sound like sz, cz, or rz take the -u ending in the Locative case. Because deszcz ends in the cz sound, it becomes deszczu.