To design is to formulate a plan using a systematic method, for the satisfaction of a human need.
In particular Machine Design is the creation of new and better machines and improving the existing ones. A new or better machine is one which is more economical in the overall cost of production and operation. The process of design is a long and time consuming one. From the study of existing ideas, a new idea has to be conceived. The idea is then studied keeping in mind its commercial success and given shape and form in the form of drawings. In the preparation of these drawings, care must be taken of the availability of resources in money, in men and in materials required for the successful completion of the new idea into an actual reality.
In designing, the particular need to be satisfied may be quite well defined, for example, a gear box is giving trouble, redesign it so it can work better, while on the other it may be vague and ill-defined that a considerable amount of thought and effort is necessary if the problems to be clear, for example many people are killed in airplane accidents.