an officer in command of a military unit
"The new commander inspected the troops before leading them into battle."
someone in an official position of authority who can command or control others
"The general appointed a new commander to lead the troops into battle."
a commissioned naval officer who ranks above a lieutenant commander and below a captain
"The new commander took over the destroyer after serving as a lieutenant commander for two years."
an officer in the airforce
"The new commander of the fighter squadron inspected the jet before takeoff."
One who exercises control and direction of a military or naval organization.
"The new commander ordered all troops to hold their positions until reinforcements arrived."
In plain English: A commander is someone who gives orders to lead a group of people or soldiers.
"The commander gave a final order before the troops marched into the forest."
Usage: Use "commander" to describe a person holding a high-ranking military or naval position responsible for leading troops or ships. Do not use it for civilian bosses unless they are specifically in charge of an armed force.
A surname.
"The Commander family has lived on this street for three generations, and their ancestral home is now a local landmark."
The word commander entered English in the late 14th century via Middle English and Old French as a noun meaning "one who commands." Although it looks like a combination of command plus -er, this formation was not actually used by speakers at the time; instead, it was borrowed directly from foreign languages where the suffix already existed.