Sentence:  Problem solving based on experience of working with other problems which share some characteristics of the current problem, but for which no algorithm is known. Good <WSD>heuristics</WSD> can reduce the time needed to solve problems by recognizing which possible approaches are unlikely to be successful. George Polya brought the notion of <WSD>heuristics</WSD> to a wide audience through his book How To Solve It. The second edition was published in 1957 and is still in print half a century later. 
Meaning of the word marked with <WSD> tags:  Heuristic methods and approaches considered collectively.