Add-on and Add ornament

Add-on noun - Something that is not necessary in itself but adds to the convenience or performance of the main piece of equipment.

Add ornament and add-on are semantically related. In some cases you can use "Add ornament" instead a verb phrase "Add-on".

Add-on and add ornament are semantically related. Sometimes you can replace phrase "Add-on" with "Add ornament", this phrases are similar.