Cad or CAD may refer to:

• Cadmium, an element
• Cold air damming, a meteorological phenomenon that involves a high pressure system
• Collisionally activated dissociation, a fragmentation method used in mass spectrometry
• Computer-aided design, a wide range of computer-based tools that assist engineers, architects and other design professionals
• Computer-assisted dispatch, a method of dispatching taxicabs, couriers, field service technicians, or emergency services
• Caspase-activated DNase, a DNase involved in apoptosis.
• Cell Adhesion axon guidance molecules that activate receptors expressed on neural growth cones.

Computer-aided design (CAD), also known as computer-aided design and drafting (CADD), is the use of computer systems to assist in the creation, modification, analysis, or optimization of a design. Computer-aided drafting describes the process of creating a technical drawing with the use of computer software. CAD software is used to increase the productivity of the designer, improve the quality of design, improve communications through documentation, and to create a database for manufacturing. CAD output is often in the form of electronic files for print or machining operations. CAD software uses either vector based graphics to depict the objects of traditional drafting, or may also produce raster graphics showing the overall appearance of designed objects.