Ergonomics: This is concerned with how easy (comfort, complexity) the product is to use by the targeted market. Physical human dimensions must be considered when designing the driver's seating, instruments, and controls in a car. Slight variations between males and females should also be kept in mind. Office furniture should be much comfortable for use over extended periods (that is, repetitive stress injuries). As far as complexity, is the operation of the device fairly intuitive, or will it require a lengthy instruction manual? Keep in mind the abilities as well as physical strength of the person that will be using the product. A home fire extinguisher should be easy enough for a child to operate.