1 If a lot of blood leaks out, it can cause a buildup of pressure in the brain because the brain is enclosed in the skull. There is no room for brain tissue to expand, and so the leaked blood can compress and kill important areas of the brain.  Hemorrhagic strokes tend to be more serious than ischemic strokes.
Horizontal definition, at right angles to the vertical; parallel to level ground. See more.
Background Essay. The physical definition of a wave is a disturbance that travels through space and transports energy. Some wavesâelectromagnetic waves (light)âcan travel through a vacuum. Other waves, known as mechanical waves, can only travel through a medium such as a solid, liquid, or gas.