The Arbitrary (standard) shape is the most popular kind of bulb. We also call them "pear shape". The number following the "A" determines the diameter of the bulb.
B and CA Shape
The B stands for "Blunt" which is different than CA shape that stands for Candelabre.those kind of bulbs are more used for decoration in a chandelier for example
The G here is really simple to keep in mind... It just meant Globe ! Most of the time you will have a number following which determines the diameter of the glass, for example : G120 means the glass of the bulb has a diameter of 120mm.
R stands for Reflector. In the conical part of the lamp a reflector is included which allow a better light scattering. The number after the "R" will indicate the diameter in millimeters of the lighting part.
Those lamps are including a Parabolic Aluminized Reflector which explain the PAR denomination. The number following describe the dimension of the lighting part of the lamp. You will also find a "S" or a "L" after the name like : PAR 30 S or PAR 30 L. This letters stand for Short and Long neck.
After the classic reflector and the parabolic reflector we have the Mirrored Reflector. This reflector is build up with a lot of small squares which direct the light exactly where you want it to be.
The Aluminized Reflector lamps are mainly used in the shop because of the precision of the beam angle thanks to the reflector. The AR111 (111mm of diameter) are the most common.
You will find the Ellipsoidal lamps most likely in the group of the gas discharge lamps.
The "T" bulb simply has a tubular shape which is more or less thicker according to the number following the "T"
Shape TEST 1/
- G - Globe
- A - Arbitrary
- R - Reflector
Shape TEST 2/
Which one is a "T" shape Lamp ?