Sinus (noun)

1. An air-filled cavity in the bones of the face that opens into the nasal passages.
2. A curved or folded shape, especially in mathematics and anatomy.

Origin:

From late latin sinus, from latin sinus, meaning "curve, bend, fold," and also "bosom, bay.".

Examples:

1. The doctor said that I had a sinus infection and prescribed antibiotics.
2. The artist was fascinated with the sinusoidal patterns found in nature.
3. The mathematician described the properties of the sinus function in his lecture.
4. The engineer was impressed with the sleek sinusoidal design of the new bridge.
5. The nurse showed the patient how to perform a sinus rinse to relieve sinus pressure.