Why do you find that most of the buildings are deprived of the 13th floor?

I am a type of word that is spelt incorrectly or used differently, on purpose for humour. What am I?
Hint 1: You can find me in a joke.
Hint 2: I am a play on words.

How many words can a pen with half refill write?

Take away my first letter, then take away my second letter. Then take away the rest of my letters, yet I remain the same. What am I?

What has many teeth, but cannot bite?

What has no start, end, or centre?

81 x 9 = 801. What must you do to make the this equation true?

Which country gets ill every time?

Which flower has two lips?

What does the rebus below mean?

TEN BADTION