Breakdown of Мы часто говорим о серьёзных темах на уроках.
мы
we
часто
often
говорить
to speak, to talk
на
on, at / by (transport) / to (a place) / to (in answer to)
Questions & Answers about Мы часто говорим о серьёзных темах на уроках.
Why do both темах and уроках end in -ах?
They are both in the prepositional plural case. In this case, most hard-stem nouns take the ending -ах, regardless of their gender. Since тема (feminine) and урок (masculine) both end in a hard consonant sound before their normal endings, they both become темах and уроках.
Why does the adjective серьёзных end in -ых?
This is the prepositional plural ending for adjectives. While nouns take -ах or -ях, adjectives take -ых or -их. Because the stem of серьёзный ends in a regular hard consonant (н), it takes the hard ending -ых to match the plural noun темах.
Why is the prepositional case used twice in this sentence?
Because there are two different prepositions triggering it. The preposition о (about) requires the prepositional case when discussing a topic (о серьёзных темах). The preposition на requires the prepositional case when indicating where an action takes place (на уроках).
The translation says "in lessons." Why does the Russian use на instead of в?