There are two ways in which a state q may be “redundant”: it is either “inaccessible” in that there is no input string that takes the start-state to q, or else it is equivalent to another state q′ in that the subsequent behavior of the machine is the same whether it is in state q or q′. In a minimal machine all inaccessible states have been dropped and all equivalent states have been merged. There is a simple algorithm that will give the minimized version of any machine. See also Myhill equivalence, Nerode equivalence.
"minimal machine." A Dictionary of Computing. . Encyclopedia.com. (August 18, 2018). http://www.encyclopedia.com/computing/dictionaries-thesauruses-pictures-and-press-releases/minimal-machine
"minimal machine." A Dictionary of Computing. . Retrieved August 18, 2018 from Encyclopedia.com: http://www.encyclopedia.com/computing/dictionaries-thesauruses-pictures-and-press-releases/minimal-machine