What is the difference between synthase and synthetase in form and activities?

Synthase is a lyase (lyase is an enzyme that catalyzes the breaking of various chemical bonds by means other than hydrolysis and oxidation, often forming a new double bond or a new ring structure) and doesn't require any energy,
Whereas
Synthetase is a ligase (ligase is an enzyme which binds two chemicals or compounds) and thus requires energy.