In a manner that is next to, beside, or adjoining; in an adjacent position or way.
From adjacent + -ly (adverb-forming suffix). This converts the adjective adjacent into an adverb describing how something is positioned or done.
When something happens adjacently—like two events occurring in adjacent rooms—the close spatial relationship can matter enormously, which is why English needs an adverb form to precisely describe this positioning.
Complete word intelligence in one call. Free tier — 50 lookups/day.