With which words we cannot use the word 'wala'? Consider the following sentences: (1) Aaj unka din hai. (2) Aaj garmi wala din hai After interchanging 'wala' we get: (1)' Aaj unka [wala] din hai. (2)' Aaj garmi [ ] din hai. (2)' doesn't make sense but why? Why can't we use 'wala' with 'garmi'. I've many other examples. (3) Vo peela gamla hai. (4) Vo kaanto wala gamla hai (3)' Vo peela [wala] gamla hai. (4)' Vo kaanto gamla hai (5) Yeh bechne wale kapre hai. (6) Yeh rangeen kapre hai. (5)' Yeh bechne kapre hai. (6)' Yeh rangeen wale kapre hai. We see that with certain words we have to use 'wala', with some words we may or may not use 'wala' and with some words we cannot use 'wala'. So what is the rule for using 'wala' in Hindi?