Online Encyclopedia
Head
In Anatomy, the head of an animal is the anterior part that bears the mouth, the brain and various sensory organs (e.g. organs of sight, hearing, smell and taste). The very simplest animals do not have a head, but most bilaterally symmetric forms do. In vertebrates the contents of the head are protected by an enclosure of bone called the skull, which is attached to the spine. The front of the human head called face.
In Society, head is often a part of a title of office, meaning "the highest". A "head of department" is thus the person with the highest standing in said department. This use might stem from the fact that the head is the highest placed part of the human body, or from the fact that the brain and therefore cognitive functions and decision making is located in the head.
The term head has a technical meaning in botany. A head is a type of inflorescence, previously known as a composite flower — a structure composed of numerous individual flowers. Species of plants of the Family Asteraceae typically have flower heads.
Some flowers with umbel s (Apiaceae) have flowers in such a proximity that they appear collectively like heads.
In fluid dynamics, head refers to the constant right hand side in the incompressible steady version of Bernoulli's equation. It is possible to express head in either meters or in Pascals (the SI unit of pressure).
This is best understood by considering a waterwheel: the head is the vertical distance from the waterwheel to the free surface of the millpond.
More generally, when considering a flow, one says that head is lost if energy is dissipated, usually through turbulence. In the context of steam trains, one talks of a good head of steam, referring to the pressure in the boiler.
In linguistics, the head is the main part of a phrase or compound. See head.
In internal combustion engines, the head refers to the part of an engine that is bolted to the engine block, over the piston cylinders. In modern internal combustion engines, the head also contains the valves, injectors, and in the case of a gasoline engine, the spark plugs. see cylinder head
In the Unix operating system, the head command provides the first few lines of a file.
Head is a surreally comic movie starring The Monkees.
In slang referring to human sexuality, head refers to the act of oral sex -- fellatio or cunnilingus. The term can be applied to the act in any gender combination. It may aloriginate from the head, or glans of the male penis. Commonly used as in "giving head" or "getting head".
Some dictionaries define close to thirty meanings of the word head. However, a majority of usages are associated with the connotation of forward, top, essential, control, etc., which are derived from attributes of an animal head (or brain). One of the few exceptions is that of the latrine of a marine vessel, which is called the head. This usage is in derived from the name of the structure projecting from the bows of sailing ships which served said purpose for the seamen.