Etymologically, AI is an acronym for Artificial Intelligence, although the original use of the term "artificial" has long been meaningless in this context. Broadly speaking, "AI"; means any non-organic sentient being, although it is most often applied to those of SI:1 or greater (in contrast to aioids). When spelt in lower case ("ai") the term can refer either to any subsingularity aioid as well.
Ais with less native intelligence than a human being are generally known as sub-turing entities; this means they are not capable of passing the so-called Turing Test. Those ais which are roughly equivalent to a baseline human in intelligence level are often referred to as turingrade; most, if not all, turingrade machines can pass the Turing Test (depending on how it is administered). Modosophont ais who are more intelligent than baseline humans but less than transapient are generally known as superturings; these superbright minds are often used even today for many complex tasks. AIs who have passed the First Singularity are known as Hyperturings.
These terms should not be confused with the term used in information technology for an idealised computer, a Turing Machine.
The types and subtypes of ai are innumerable (far more than even the billions of known biological species), although these can generally be reduced to a few basic categories. Some are able to expand their capabilities exponentially, while others are more limited. Some work to actively reproduce themselves, while others merely maintain their own existence or may even be self destructive. Some ais, although quite intelligent, have reasoning abilities directed along narrow channels, as for instance an ai 'slaved' for a particular task, even a highly complex task such as piloting a ship, air traffic control or safekeeping a hab.