This is the 40th most frequent Hindi word.
वजह
Reason.
Here, 'वजह' denotes the cause of the increase in health issues, which is pollution.
प्रदूषण की वजह से स्वास्थ्य समस्याओं में वृद्धि हो रही है।
Due to pollution, health issues are increasing.
'वजह' in this example points to the reason he arrived late, which is traffic.
ट्राफिक की वजह से वह देर से पहुँचा।
He arrived late because of traffic.
In this sentence, 'वजह' refers to the cause or reason behind starting the task, which led to learning extensively.