is a term indicating that the state of something, which is normally open, is now totally closed.
- In medicine, the term is often used to refer to blood vessels, arteries or veins which have become totally blocked to any blood flow. For issues of artery occlusion, see stenosis, atheroma, and coronary catheterization.
- In dentistry, occlusion refers to the manner in which the teeth from upper and lower arches come together when the mouth is closed.
- In psychology, specifically memory research, occlusion is the phenomenon of items associated to the same cue as the target blocking the successful retrieval of that target, through strength dependent response competition. The tip-of-the-tongue phenomenon is an example of occlusion.
- In meteorology, the term refers to the complex frontal structure formed when a cold front overtakes a warm front. It is associated with widespread, steady rainfall in advance of the occluded front. In addition to extratropical cyclones on the synoptic scale, occlusions also occur on the mesoscale, as when a rear flank downdraft occludes in a supercell thunderstorm.
- In computer graphics, the term is used to describe the manner in which an object closer to the viewport masks (or occludes) an object further away from the viewport. In the graphics pipeline, a form of occlusion culling is used to remove hidden surfaces before shading and rasterizing take place.
- In audiology, occlusion refers to the phenomenon that when persons with normal hearing close off the opening into the ear canal, the loudness of low pitched sounds (presented by bone conduction) increases.
- In computer gaming audio engines, the term describes modification of the qualities of a sound that passes through or around an object so that the player experiences a greater sense of realism. For example, a sound that comes from behind a door realistically sounds as if it passed through a door.