Senior has 8 different meanings across 3 categories:
Noun · Adjective · Proper Noun
an undergraduate student during the year preceding graduation
"As a senior, I'm spending my last semester on campus before heading off to graduate school next summer."
An old person.
"The senior sat quietly on his porch, watching the autumn leaves fall around him."
In plain English: A senior is an older person who has held a job or position for a long time.
"The senior at the graduation ceremony received her diploma with her family."
used of the fourth and final year in United States high school or college
"the senior prom"
Older; superior
"The senior manager advised the junior staff to submit their reports before noon."
In plain English: Senior describes someone who is older than others in their group or has held a position for a long time.
"The senior students led the new ones around the campus."
A surname.
"The meeting was chaired by Mr. Senior, whose family has owned the bakery for four generations."
The word "senior" comes from the Middle English term senior, which was borrowed from the Latin comparative adjective senior meaning "older." It is derived from the root senex, referring to age or being old.