Step 1: Definition:
A nation is a large group of people who see themselves as a single political community, sharing a common territory, history and culture.
Step 2: Key feature:
It is held together above all by a shared political consciousness and the aspiration to (or possession of) a sovereign state, rather than by any one objective marker like language or religion alone.
Final Answer:
A nation is a self-conscious political community bound by shared identity, territory and the will to have (or maintain) its own sovereign state.