DO: Diffractive Optics.
EF: Electro-Focus. Refers to the focus motor built into the lens that is common to all EOS-mount lenses.
EF-S: Electro-Focus Short Back Focus. Canon's new lines of lenses made specifically for small-sensor EOS digital cameras.
EOS: Electro-Optical System. Refers to Canon's series of SLR cameras that are capable of auto-focusing.
IS: Image Stabilizer
L: Luxury. Designation for Canon high-end lenses.
USM: Ultrasonic Motor. In-lens focusing motor that is super quiet and is based on electro-magnetic field to operate.
MD: Indicates Minolta lenses that could be used on late model, manual focus Minolta SLR's for shutter priority auto-exposure. Minolta or independent service centers could upgrade most MC lenses to MD specs.
AF-I: Autofocus Internal Motor. The AF motor is in the lens, rather than in the camera body.
AF-S: Autofocus Silent Wave Motor. AF-S is similar to Canon's USM and Sigma's HSM technology. Developed to provide the same benefit to Nikon users and to compete with USM and HSM.
DC: Defocus Control.
ED: Extra-low Dispersion. Lens element to help correct chromatic aberrations.
G: Designates D-type lenses with camera controlled aperture settings only. Its benefit includes lighter and smaller lenses.
IF: Internal Focus.
Micro: Same as macro.
AL: Aspherical Lens.
ED: Extra low Dispersion. Lens element to help correct chromatic aberrations.
J: Lenses without external aperture ring; camera controlled aperture.
Sigma provides a full descriptive list of acronyms it uses. The list is located in the "Related Links" section.
DC: Sigma lenses made for small-sensor digital cameras.
DF: Dual Focus.
DG: Lenses adapted to be useable on both digital and film cameras.
DL: Deluxe. Indicates Sigma low-end lenses.
EX: Excellence. Indicates Sigma high-end lenses that are marketed to the professionals.
HSM: HyperSonic Motor. HSM is similar to Canon's USM technology. Developed to provide benefit to Sigma users and to compete with USM.
HZ: Hyperzoom. Lenses with extended zoom and focusing range.
AIS: Active Interface Shoe. AIS is a 16-pin proprietary electro-mechanical hot shoe that can accept a variety of accessories, such as microphone and light. The accessories are fully powered by this interface and require no battery of its own. Due to the sophisticated interface, AIS accessories can perform a number of specialized features that non-AIS accessories cannot.
Di: Lenses with optics designed to combat increased reflectivity of digital sensors.
ATX: Advanced Technology-Extra.
SZX: Manual focus lenses.