Mass emigration: Large-scale movement of people from one country to another. During the Great Irish Famine, there was a significant mass emigration from Ireland to other countries.
Push factors: Negative factors or conditions that force people to leave their homes or homeland. In this case, the dire circumstances created by the famine acted as push factors for Irish people to migrate.
Diaspora: The dispersion or scattering of a population beyond its original homeland. The Great Irish Famine led to a significant Irish diaspora as many people left Ireland seeking better opportunities elsewhere.