Definition of a Photon. A photon is the quantum of electromagnetic radiation. The term quantum is the smallest elemental unit of a quantity, or the smallest discrete amount of something.
General of the Army(GA) is a five-star general officer and is the second highest possible rank in the United States Army. A special rank of General of the Armies, which ranks above General of the Army, does exist but has only been conferred twice in the history of the Army.
General officers (those with the word General in the rank) are anything from grades O-7 to O-10. The names that go with these grades are Brigadier General, Major General, Lieutenant General, and General. I believe these same names and grades apply in the US Army and Marine Corps.