Universal Grammar is made up of a set of rules that apply to most or all natural human languages. Most of these rules come in the form of "if a language has a feature X, it will also have the feature Y." Rules that are widely considered as part of UG include: If a language is head-initial (like English), it will have prepositional phrases; if and only if it is head-final (like Japanese) will it have post-positional phrases.[13] If a language has a word for purple, it will have a word for red.