Sinus/ˈsaɪnəs/ Definition 1 of 3Pro Tip 1/3Biological Feature Refers to natural structures in the body, mainly around the nasal area. Sinus issues can cause breathing problems. Pro Tip 2/3Specific Symptoms Often associated with specific health problems like congestion and headaches. A sinus headache can be quite painful. Pro Tip 3/3Not Always Sinuses The word 'sinus' might incorrectly be used for any headache or facial pain. Not every forehead pain is a sinus issue.