Something is best if nothing is better than it. When you win a competition, it means you are the best.
The opposite of best is worst.
Something is clean if it has no dirt or marks to spoil its looks, and it is neat and tidy. The opposite of clean is messy or dirty.
Cis forComfortable
Something is comfortable if it feels nice to use. You are comfortable if you feel good and at ease while doing something. The dog in the picture is in a very comfortable chair.
Something is delicate if it has fine detail, or is fragile. A color or flavor is delicate if there is only the barest hint of it.
Something or someone is elegant if it is gracefully refined and dignified.