Platoon

A platoon is a military unit that in size and organisation is between a squad and a company.

Breen Confederacy
A trun (plural trunhn) is the Breen equivalent of a company or large platoon and comprised of between 50 - 300 soldiers commanded by a ak'trun (captain/lieutenant). 

Cardassian Union
A mezreko was the Cardassian equivalent to a platoon and was made up of around 40 soldiers commanded by a glinn. 

Dominion
A platton in the Dominion is comprised of three squads numbering 9 Jem'Hadar and commanded by a Rona'atorn. 

Klingon Defense Force
A Klingon Defense Force platoon is approximately 25 warriors commanded by a Sogh (lieutenant). 

Romulan Star Empire
A rost'val is the Romulan equivalent to a platoon and was formed around a group of squads and was between 20 - 50 soldiers with a lieutenant or captain in command. 

Starfleet Ground Forces
A Starfleet Ground Forces platoon is between 20 and 60 Starfleet soldiers (two to five squads) and is typically commanded by a lieutenant JG or lieutenant. (LUG RPG: )

Starfleet Marine Corps
A Starfleet Marine Corps platoon is between 20 and 60 Starfleet Marines and is typically commanded by a first lieutenant.