A Platoon is a military unit used by the UNSC Marine Corps to organize its combat forces and is composed of three to four squads.
The typical platoon is composed of three squads for a total of 36 soldiers. It is commanded by a Second Lieutenant, who is assisted by a Platoon Sergeant of either Sergeant or Staff Sergeant rank.
ODST Platoons seem to have fewer members than the regular marine units, possibly because they aren't as easily defeated in battle, making it more efficient to deploy them in smaller forces.
105th Drop Jet Platoon