multitude (of sth/sb): an extremely large number of things or people Examples: a multitude of possibilities a multitude of birds These elements can be combined in a multitude of different ways. The region attracts tourists in their multitudes. .......................................... host of sb/sth : a large number of people or things Example: a host of possibilities

I wished people would ask how are they similar more often. Then I can just give one or two word answers and say: a lot :P

multitude = many (abstract) host = many things (less abstract)