Identify the conceptual definition that most accurately and comprehensively encapsulates the modern political doctrine of 'Citizenship':
1. A formal legal status denoting full and equal membership within a structured political community, binding the individual to reciprocal rights and duties.
2. A sociological indicator describing the collective relationship established between a culturally homogeneous community and a nation-state.
3. An exclusive legal designation granted only to demographics possessing a shared historical lineage and unified cultural heritage.
4. A purely symbolic certificate issued by a government guaranteeing the absolute equality of economic status among all residents.