The human body is the entire structure of a human organism and comprises a head, neck, torso, two arms and two legs. By the time the human reaches adulthood, the body consists of close to 100 trillion cells, the basic unit of life. These cells are organised biologically to eventually form the whole body.
Facial hair is a secondary sex characteristic of human males. Men typically start developing facial hair in the later years of puberty or adolescence, between seventeen and twenty years of age, and most do not finish developing a fully adult beard until their early twenties or later. This varies, as boys may first develop facial hair between fourteen and sixteen years of age, and boys as young as eleven have been known to develop facial hair. In addition, the patches of hair can vary between bushy and bristly. Women are also capable of developing facial hair, especially after menopause, though typically significantly less than men.
Male pogonotrophy (the growing of facial hair; i.e., beardedness) is often culturally associated with wisdom and virility. Men may style their facial hair into beards, moustaches, goatees or sideburns; others completely shave their facial hair. The term "whiskers," when used to refer to human facial hair, indicates the hair on the chin and cheeks.
A safety razor is a shaving implement with a protective device positioned between the edge of the blade and the skin. The term was first used in a patent issued in 1880, for a razor in the basic contemporary configuration with a handle attached at right angles to a head in which a removable blade is placed (although this form predated the patent). Its edge was protected by a comb patterned on various types of protective guards that had been affixed to open-blade straight razors during the preceding decades. Some safety razors in present-day production retain a comb but the more common protective device is now a solid safety bar. The initial purpose of these protective devices was to reduce the level of skill needed for injury-free shaving, thereby reducing the reliance on professional barbers for providing that service and raising grooming standards. Prior to the introduction of the disposable razor blade by King C. Gillette in 1901, however, safety razor users still needed to strop and hone the edges of their blades. These are not trivial skills (honing frequently being left to a professional) and remained a barrier to the ubiquitous adopting of the be your own barber ideal.
In the context of machining, a cutting tool (or cutter) is any tool that is used to remove material from the workpiece by means of shear deformation. Cutting may be accomplished by single-point or multipoint tools. Single-point tools are used in turning, shaping, plaining and similar operations, and remove material by means of one cutting edge. Milling and drilling tools are often multipoint tools. Grinding tools are also multipoint tools. Each grain of abrasive functions as a microscopic single-point cutting edge (although of high negative rake angle), and shears a tiny chip.
Cutting tools must be made of a material harder than the material which is to be cut, and the tool must be able to withstand the heat generated in the metal-cutting process. Also, the tool must have a specific geometry, with clearance angles designed so that the cutting edge can contact the workpiece without the rest of the tool dragging on the workpiece surface. The angle of the cutting face is also important, as is the flute width, number of flutes or teeth, and margin size. In order to have a long working life, all of the above must be optimized, plus the speeds and feeds at which the tool is run.