# How to Choose if a reaction will go elimination of substitution? [closed]

I want to know how to choose if a given reaction will prefer going substitution mechanism or elimination mechanism.Both elimination and substitution reactions have types like Sn1 ,Sn2 ,SnNGP,Sni and E1 ,E2 ,E1CB

I know how to decide (if given that reaction is substitution reaction or elimination reactiin) which type among these a given reaction will go but I am always confused on choosing that the reaction will be substitution or elimination.

Any help/contribution appreciated.Thanks!