How many types of essential amino acids do humans require from their diets?

The answer to this question would be nine amino acid.

Essential amino acid is the amino acid that can't be produced by a human, so it needs to be fulfilled by their diet. There are 9 essential amino acid which was phenylalanine, methionine, leucine, valine, threonine, tryptophan, isoleucine, lysine, and histidine 
But there are 6 conditionally essential amino acid that the synthesize might no be enough in some condition, so it will be needed in the diet too.