Aware of or knowledgeable about a subject; informed or up to date on a particular topic.
2.
generalneutral
Located on the upper surface of or at a higher position of something; situated atop a place or feature.
3.
generalneutral
Used as part of phrasal verbs (verb + up on) to indicate examination, supervision, or monitoring of a person or thing.
4.
generalneutral
Used after a verb in combination with a temporal expression to indicate the time or occasion when an action occurs (equivalent to 'on' when specifying a day or date).
5.
generalneutral
Used in resultative constructions (as in 'end up on') to indicate the final state, condition, or location reached by someone or something.