Have you ever used a lamp size term and wonder why it is called that way? Well, wonder no more!

Lamps are named based on their shape and size (width) in inches (1/8"). This is why you will find terms such as A19, PAR16 or even GU10. The first letter or letters determine the type of lamp and or shape. Here is a list of terms and abbreviation use to describe the lamp shape and/or the base type: 

Lamp-shapes-sizes