centenarian

As a noun centenarian is

one who is at least 100 years old one who is past his or her tenth decade.

As an adjective centenarian is

being at least 100 years old beyond one's tenth decade.

As nouns the difference between taxonomy and centenarian

is that taxonomy is the science or the technique used to make a classification while centenarian is one who is at least 100 years old one who is past his or her tenth decade.

As an adjective centenarian is

being at least 100 years old beyond one's tenth decade.

As nouns the difference between centenarian and centennial

is that centenarian is one who is at least 100 years old. One who is past his or her tenth decade while centennial is the hundredth anniversary of an event or happening.

As adjectives the difference between centenarian and centennial

is that centenarian is being at least 100 years old. Beyond one's tenth decade while centennial is relating to, or associated with, the commemoration of an event that happened a hundred years before.