Some common reasons include: 1  a serious accident â such as a road accident, a severe head injury, a serious fall or severe burns. 2  a serious short-term condition â such as a heart attack or a stroke. 3  a serious infection â such as sepsis (blood poisoning) or severe pneumonia.
The definition of unnecessary is not needed. An example of something unnecessary is a bowl of sugar for cooking meatballs.
something that obstructs or hinders progress. Obstacle, obstruction, hindrance, impediment refer to something that interferes with or prevents action or progress. An obstacle is something, material or nonmaterial, that stands in the way of literal or figurative progress: Lack of imagination is an obstacle to one's advancement. An obstruction is something that more or less completely blocks a passage: A blood clot is an obstruction to the circulation.