SUD shares with with UD its compound relation, though the exact usage of this relationship is determined on a language-by-language basis. SUD annotations for some languages, such as French, do not use the compound relation at all.

Naija in particular makes heavy use of this relation, which is used to link nouns to virtually any other nouns which play a modifying role. However, it is also used to annotate phrasal verbs as well as a more limited subset of relations between nouns and adjectives, such as dry cleaner, which are considered fixed expressions whose meaning cannot be directly understood from its constituent parts. For more information about use of this relation in Naija, please consult the language’s dedicated page.

In many cases, the existence of a compound relation can be determined with a series of linguistic tests. For example, it might be impossible to insert an adjective between two elements of a compound. In English, compounds are phonologically distinct, pronounced with an intonation similar to that of a single word. Consider the difference in pronunciation between real estate, a bona fide compound, and real property, an adjective and a noun connected with a simple mod relation.


The flat relation plays a similar role, and its exact usage also varies on a language-by-language basis. However, it is most frequently used to connect the various elements of proper names to one another, including titles and honorifics.

The flat relation can also be used to link individual elements of numbers to one another.