После тренировки сестра вернулась в раздевалку и забыла ключ от шкафчика.

After the workout my sister went back to the locker room and forgot the key to her locker.

Breakdown of После тренировки сестра вернулась в раздевалку и забыла ключ от шкафчика.

• в: to
• и: and
• сестра: the sister
• ключ: the key

Questions & Answers about После тренировки сестра вернулась в раздевалку и забыла ключ от шкафчика.

Why is тренировки in the form тренировки?

Because после always requires the genitive case in Russian.

• тренировка = training / practice / workout
• Genitive singular: тренировки

So:

• после тренировки = after the training / after practice

This is a very common pattern:

• после урока = after the lesson
• после работы = after work
• после школы = after school

So the learner should remember: после + genitive.

Why is it сестра, not some other form?

Сестра is the subject of the sentence, so it is in the nominative case.

Here, сестра means sister, and it is the one doing the actions:

• she returned
• she forgot / left behind the key

So nominative is used because it answers who did it?
→ сестра

Why is the verb вернулась feminine?