Enormous : extremely large

   Vd: -  an enormous car/house

         - He earns an enormoussalary.

         - You've been an enormous help.

Vast : of very great size or amount

    Vd:  - A vastaudiencewatchedthe broadcast.

           -  The amount ofdetailthe bookccontains is vast.

           -  The peoplewho have takenouradvice havesavedthemselves vast amounts/sums of money.

           - The vast majority of children attend state schools.
Extensive : covering a large area

    Vd: - a school with extensive groundsextensive repairs to the motorway

          - Her knowledge of music is extensive .

          - The wedding received extensive coverage in the newspapers (= it was written about a lot).

Masive: very large in size, amount, or number

     Vd:  - They have a massive house.

            - She died after taking a massive overdose of drugs.

            - If the drought continues, deaths will occur on a massive scale.