Evolution of love

NOTHING CAN BE DEFINED:

When I was studying in school, once the teacher asked the students in the class to define a chair.
One student told that chair is a thing which has four legs.
Then the teacher replied that a table and a cot also have four legs.
Then I stood up and told that chair is a thing on which we sit.
Then the teacher replied that we sometimes happen to sit on fellow
passengers in a bus. Later, I realized that chair cannot be defined
and also nothing can be defined.