"A nation is a grouping of people who share real or imagined common history, culture, language or ethnic origin, often possessing or seeking its own government".
"A part, or division, of the people of the earth, distinguished from the rest by common descent, language, or institutions; a race; a stock"
And so on and on, but what all these definitions are trying to covey this, that, people who are alike in there history, culture or language are considered to be a nation.
There are counter definitions too, in which emphasis is on that, inhabitants of same land with keeping difference in there language, history and culture but governed by a same system are considered as nation.America is one of its example.
But when similarities are weak then differences then it will not be considered as a nation, and so the case of Pakistan is.
We are groups of people with different approaches our interests.
The only similarity is religion but it also subdivided in sects which creates a difference, then language , norms and culture history.
So all these things which exist here are trying to say that we are groups of people with differences but live and governed by same state and fallow the same rule of state.
So on one hand we are a nation and other hand we are not a nation.