A type "C" light bulb is a cone-shaped light bulb that is designed for small appliances and indicator lamps. The "C" refers to the cone shape of the bulb. There are many different kinds of "C" light bulbs. However, they generally fall into two categories: decorative and regular.
C-shaped light bulbs with blunt tips are sometimes referred to as torpedo shaped, or bullet, light bulbs. C-shaped bulbs with molded, bent "flame tips," are also known as chandelier light bulbs. There are several different versions of the C-shaped bulb which are denoted by a numeral following the letter "C". Though most often used for decoration, these bulbs are also used in marquees, electronic signs and scoreboards.
Different "C" light bulb models include C7, CA5 and CA10. The number in the light bulb type description refers to the size of the bulb at its widest point in eighths of an inch. For example, a C7-sized light bulb is .875 inches wide at its largest point.
The "A" in CA light bulbs refers to the decorative, flickering filament inside the cone-shaped bulb. This is why "C" type bulbs that contain an "A" in their type descriptions are referred to as candles.