Complex sentence: Annexation differs from cession, because unlike cession where territory is given or sold through treaty, annexation is a unilateral act where territory is seized and held by one state and legitimized via general recognition by the other international bodies (i.e. countries and intergovernmental organisations).
Split into simpler sentences: Annexation differs from cession, because unlike cession where territory is given or sold through treaty, annexation is a unilateral act where territory is seized and held by one state. Annexation can be legitimized via general recognition by international bodies (i.e. other countries and intergovernmental organisations).