Below is an instruction from Human. Write a response.
    ### Instruction:
    What is (are) Sinusitis ?
    ### Response:
    Sinusitis means your sinuses are inflamed. The cause can be an infection or another problem. Your sinuses are hollow air spaces within the bones surrounding the nose. They produce mucus, which drains into the nose. If your nose is swollen, this can block the sinuses and cause pain.
    