The 'nature' group
These nouns are used to indicate why, or in what respect, someone or something is what they are. We include here reputation, which indicates that a person or thing is thought to be something, and definition, which indicates that a person or thing must be something because of the way they are described. Definition, profession, reputation, and trade are count nouns. Nature is a singular noun.
by adoption by birth by blood by conviction by definition by inclination by instinct by marriage by nature by profession by reputation by temperament by trade by tradition by training
Youngsters are conservative by nature and can take a dim view of a new teacher suddenly turning up.
A lawyer by profession, he came to national prominence as the Secretary General of the National Union of Mineworkers.
She was by reputation a good organiser and committee person.