IPA: /əˈpɒzɪtnəs/
KK: /əˈpɑːzɪtnəs/
The quality of being relevant or suitable for a particular situation or purpose.
The appositeness of her comments made the discussion much more engaging.
Appositeness is formed from "apposite" (from Latin "appositus", meaning placed near or appropriate) and the suffix "-ness" (meaning the state or quality of). The word refers to the quality of being appropriate or relevant to a particular situation.
Think of something being 'placed near' or 'appropriate' — that's what appositeness means, the quality of being suitable for the context.