The word "design" has many meanings. A digest of various dictionary definitions is: to plan, conceive, invent, and to designate so as to transmit the plan to other.
Design, from the Latin "designare" (to mark out), is the process of developing plans, schemes, directions, and specifications for something new. Design is distinguished from production and craftsmanship: design is the creative original plan, and the production and craftsmanship are a part of the execution of the plan [2].
Design is a word used more or less loosely in all the arts in referring to composition, style, decoration, or any relationship of the parts of a complete entity. In some areas, notably in architecture and in product design, art and engineering affect each other, so that complete freedom is often somewhat restricted. Usually, painters, poets, musicians, and some others can design with great freedom [6].
Design may be presented by means of drawings, models, patterns, specifications, results of calculations, or other similar methods of communication.
Logically, one who designs is called a designer. All designers must be experienced and educationally organized and oriented. In other words a designer must know a great deal about what he is attempting to design or he will fail miserably [6].
Mechanical design means the design of things and systems of a mechanical nature- machines, products, device, and instruments. For the most part, mechanical design utilizes mathematics, the materials sciences, and the engineering-mechanics sciences. Mechanical engineering design includes all mechanical design, but it is a broader study, because it includes all the disciplines of mechanical engineering, such as the thermal and fluids sciences, too. Design of machine elements is an integral part of the larger and more general field of mechanical design. Designers and design engineers create devices or systems to satisfy specific needs. Mechanical devices typically involve moving parts that transmit power and accomplish specific patterns of motion. Mechanical systems are composed of several mechanical devices.

2.2.1 The Phases Of Design
The total design process is of interest to us in this chapter. How does it begin? Dose the engineer simply sit down at his or her desk with a blank sheet of paper and jot down some ideas? What happens next? What factors influence or control the decisions, which have to be made? Finally, how dose this design process end? The complete process, from start to finish, is often outlined as in Fig. 1-1. The process begins with recognition of a need and a decision to do something about it. After much iteration, the process ends with the presentation of the plans for satisfying the need [2].
Fig. 1-1 The phases of design