The Canon EOS (Electro-Optical System) is an autofocus 35 mm film and digital SLR camera system that was introduced in 1987 with the Canon EOS 650 and is still in production as Canon's current dSLR system. The acronym EOS was chosen for Eos in Greek mythology, and is often pronounced as a word (i.e., EE-oss), although some spell out the letters, reading it as an initialism. Both pronunciations are acceptable as there is no official pronunciation.
It competes primarily with the Nikon F series and its successors, as well as autofocus SLR systems from Olympus Corporation, Pentax, Sony/Minolta, and Panasonic/Leica. In most countries, EOS cameras have the largest market share of SLR cameras.[source?]