Master is the top o the pile of deck officers aboard ship and thus is the most senior
the chief mate is a senior officer and just below the master
2nd, 3rd mates are often all considered as junior officers although it isn’t really appropriate to consider any well seasoned mate as being a junior but they still aren’t senior either. The 3rd mate with the least amount of seatime is the most junior of the deck officers on a ship.
The absolute bottom of the pile is the deck cadet who is the lowest of lowly worms and needs to be kicked at every opportunity just because…
Nuts to you Shellback…it was meant with humor. I was a deck cadet once upon a time myself in the bad old daze when ships were steampowered and chief mate’s ate us for breakfast after their obligatory coffee and cigarette eye openers!