|This article/section is a stub — probably a pile of half-sorted notes and is probably a first version, is not well-checked, so may have incorrect bits. (Feel free to ignore, or tell me)|
Things that add context/explanation/definition/description/name.
In English (and presumably in general), appositional modifiers are typically placed directly next to the thing (noun/nominal?) they augment.
- the parenthetical in "John, a mathematician, has a habit of mumbling" adds contextual information to John
- abbreviations next to their expansion
- in men and women, both are put it a more limited and specific context, which suggests that in this context we are grouping or distinguishing gender.
- In The name John stands for ..., name is an appositional modifier for John
Appositions are used to help clarify and/or disambiguate.
(not to be confused with adpositions)