The politically correct term for aging is "older adults" or "seniors." This terminology is preferred as it focuses on the stage of life rather than perceived limitations associated with aging.
You can refer to a person in their 70s as a septuagenarian.
A person who is retired is simply referred to as a retiree.
A grown person is typically referred to as an adult.
A person of whom you are a guardian is typically referred to as a ward.
A person who studies genealogies is a genealogist.
A person who studies philosophy is called a philosopher.
A person who studies organisms is called a biologist.
a person who studies people but not an psychologist
a person that studies gems is called a gemologist.
what do you call somebody who studies snails.
A person who studies birds is called an ornithologist.
A person who studies birds is called an Ornitholoigst
A person who studies poisons is called a toxicologist.
A person who studies lichens is called a lichenologist.
A person who studies theology is called a theologian.
A person who studies the mind is called a psychologist.