In linguistics, subordination (abbreviated variously , , or ) is a principle of the hierarchical organization of linguistic units. While the principle is applicable in semantics, syntax, morphology, and phonology, most work in linguistics employs the term "subordination" in the context of syntax, and that is the context in which it is considered here. The syntactic units of sentences are often either subordinate or coordinate to each other. Hence an understanding of subordination is promoted by an understanding of coordination, and vice versa.