nomenclature - What is the difference between a phosphoryl group and a phosphate group?

I am looking at covalent modification of enzymes and I found out that only one of these types is phosphorylation. But I do not understand what the difference between the a phosphate and a phosphoryl group is in terms of nomenclature.

Answer

The difference is basically one oxygen atom. If you consider monoethyl phosphate as an example, the ethyl alpha-carbon bears a phosphate group, whereas the ethoxy oxygen bears a phosphoryl group.