Do cats feel lonely when they live alone?
Yes, cats do have a social nature, and they can get bored when left alone at home. Most cats will pass the time by sleeping, waiting for their owners to come home. They'll wake up when you're almost home and sit waiting for you. Cats that don't receive enough companionship from their owners for extended periods are more likely to develop depression. 
If you're still worried about your cat being lonely, you can get another one. Two cats at home will definitely keep it company, and the short day will pass quickly.
Extended Information
Cats groom themselves frequently. Kittens, in particular, are very protective of their bodies and groom themselves. After eating, cats will wipe their whiskers with their front paws, and after being held, they will lick their fur. This is a cat's instinct, used to remove odors and avoid being tracked by predators. A cat's tongue has many rough little bumps, making it an ideal tool for removing dirt.
After being petted by its owner, the cat will notice the spot where it was petted: the cat is memorizing the person's scent because it worries about not being able to find its owner if separated. Many people mistakenly believe this is because the cat thinks it's dirty.
