You can sometimes give an adjective the opposite meaning by putting 'un' in front of it. 'Comfortable' means relaxed and at ease. 'Uncomfortable' means the very opposite.
All the adjectives in the sentences below can be made to mean the opposite by adding 'un' to them.
1. It is very fair of you to say that about your best friend.
2. This new chair is comfortable.
3. He leads a stable lifestyle.
4. Her clothes are fashionable.
5. What you said about him was true.
6. He is selfish with everyone in the family.
7. My brother is fit to run the marathon.
8. I feel equal to my brother in every way.
1. unfair/2. uncomfortable/3. an unstable/4. unfashionable/5. untrue/6. unselfish/7. unfit/8. unequal