What Is Sinusitis?
Sinusitis is inflammation or infection of any of the four groups of sinus
cavities in the skull, which open into the nasal passages. Sinusitis is
not the same as rhinitis, although the two may be associated and their
symptoms may be similar. The terms "sinus trouble" or "sinus
congestion" are sometimes wrongly used to mean congestion of the
nasal passage itself. Most cases of nasal congestion, though, are not
associated with sinusitis.