A language is head-marking if the grammatical marks showing agreement between different words of a phrase tend to be placed on the heads (or nuclei) of phrases, rather than on the modifiers or dependents. Many languages employ both head-marking and dependent-marking, and some languages double up and are thus double-marking. The concept of head/dependent-marking was proposed by Johanna Nichols in 1986 and has come to be widely used as a basic category in linguistic typology.