People that are fifty years old well you call them old people or grandma....
After 55 you are a senior. Medically an older person is called geriatric.
A sexagenarian
Sex person
a believer
Agnostic.
Haji
A person who is a quinceanera is a girl from a Latin American Country celebrating her 15th birthday.
A pilgrim is a person who travels for religious reasons.
A sexegenarian.
"Centenarian" is usually used for anyone one hundred or older.
Coal miner. An older term is "collier."
Such a person is a centenarian.
19 is legally an adult in almost every country. You'd call them either a man or a woman.
sixty undecillion
no number
quinquagenarian
Centenarian
A centenarian.
Old
The younger person is always introduced to the older person. Mrs Smith, may I introduce (my niece) Mary Jones. Mary this is Mrs. Smith. Use the name the younger person should call the older as a courtesy to them. You may add relationships as I have in brackets if they are relevant.