This is the 251st most frequent Hindi word.
जब
"When."
In this sentence, 'जब' introduces a specific time in the past as a subordinate conjunction.
जब मैं दिल्ली गया, तब बारिश हो रही थी।
When I went to Delhi, it was raining.
Here, 'जब' is used to signify the specific occasion on which the event occurred.
वह तब खुश हुआ जब उसने परीक्षा पास की।
He became happy when he passed the exam.
In this sentence, 'जब तक' is used to set up a condition of time span.