Definition
Phrases adding other details to the main argument are adjuncts. (Gibson, 1973, p. 66) They refer to other participants, time, location and manner concerning an event. (Gibson, 1973, p. 75) They may precede or follow the center and its complements. (Gibson, 1973, p. 70)
In Halkomelem, there exists nominal, verbal and adverbial adjuncts. (Suttles, 2004)
Examples

References
Suttles, W. (2004). Musqueum reference grammar. UBC Press. SFU Student Access.