Grammatical use of ''IN''

 Three functions of “in” as a prefix

1. When “in” is added to a word at the beginning, it might generate the direct opposite of such words:Formal- informal.Valid   Invalid
2. When “in” is added to a word at the beginning, it can have the same meaning as the word it is added to:
   Flammable- inflammable.
   Note that both flammable and inflammable mean that something can be easily set on fire.

When “in” is added to a word at the beginning, it might amplify the meaning of the word it is added to:
Value- invaluable.
Note that to be invaluable means to be of great value: Mallam MukhtarMaruf Abdul Azeez is my invaluable fan

GAB