simplification; unification
racially homogeneous; monoracial
ethnically homogeneous nation; racially homogeneous nation
monolingual; homogeneous (language)
single market (e.g. European single market)
single currency; currency unification
monoculture; monocropping
single attachment concentrator
single attachment station
Out-of-Africa theory (positing a recent African origin for modern humans)
single step operation; step-by-step operation
single point of failure; SPOF