Relating to or involving adjection; of the nature of adding or joining something to something else.
From Latin 'adjectio' (an adding) plus the English suffix '-al' (relating to). This creates an adjective describing the process or quality of joining things together.
This is a rare word because English prefers 'adjunctive' instead—it shows how languages constantly shuffle which words survive in actual use, and some perfectly logical formations just lose the popularity contest over time.
Complete word intelligence in one call. Free tier — 50 lookups/day.