This is about verb 'pyaas lagna'. अचानक उसे मालूम हुआ कि बहुत देर से उसे प्यास नहीं लगी है*(NOT hain हैं) "Suddenly she came to know that for a very long time she had NOT felt thirsty" pyaas lagna - to feel thirst. pyaas nahin lagna - to NOT feel thirst. If I feel like drinking water, in hindi, I will say - मुझे प्यास लगी है. Mujhe pyaas lagi hai i.e. I am thirsty or I am feeling thirsty If I am not thirsty, मुझे प्यास नहीं लगी है. Mujhe pyas NAHIN lagi hai - I am not thirsty Similarly, he/she is thirsty उसे प्यास लगी है he/she is NOT thirsty उसे प्यास नहीं लगी है