Stenosis (from Ancient Greek στενός (stenós) 'narrow') is the abnormal narrowing of a blood vessel or other tubular organ or structure such as foramina and canals.

[3] Stricture as a term is usually used when narrowing is caused by contraction of smooth muscle (e.g. achalasia, prinzmetal angina); stenosis is usually used when narrowing is caused by lesion that reduces the space of lumen (e.g.

[6][7] Restenosis is the recurrence of stenosis after a procedure.

[8] Examples of vascular stenotic lesions include: The types of stenoses in heart valves are: Stenoses/strictures of other bodily structures/organs include: Stenoses of the vascular type are often associated with unusual blood sounds resulting from turbulent flow over the narrowed blood vessel.

This sound can be made audible by a stethoscope, but diagnosis is generally made or confirmed with some form of medical imaging (such as ultrasound).