Questions & Answers about जब मेरी बहन उदास होती है, तब वह कमरे में बैठती है।
जब ... तब is a common Hindi correlative pair meaning when ... then or whenever ... then.
So:
- जब मेरी बहन udās hotī hai = when/whenever my sister is sad
- तब वह कमरे में बैठती है = then she sits in the room
In English, we often do not say then, but Hindi often uses तब to neatly match जब.
You can also very often omit तब in natural Hindi:
- जब मेरी बहन उदास होती है, वह कमरे में बैठती है।
That still sounds correct.
Here होती है comes from the verb होना (to be / to become / to happen, depending on context).
In this sentence, उदास होती है means is sad in a habitual or repeated sense.
So it is not talking about one exact moment only. It means something like:
- When my sister is sad
- or more naturally, Whenever my sister feels sad
Because the subject बहन is feminine singular, the verb form is also feminine singular:
- masculine singular: होता है
- feminine singular: होती है