THIS  IS  the eighth collection of my Mathematical Games col-umns that have been appearing monthly in  Scientific Americansince December  1956.  As in previous volumes, the columns havebeen corrected, updated, and enlarged to include bibliographiesand valuable new material provided by loyal readers.One of those readers, not mathematically inclined but wholikes to read the columns nonetheless, has often asked: "Whycan't you, as a favor to readers like me, give us a glossary ofsome of the terms you frequently use but seldom define?"Okay, dear reader-here  it is. The terms alphabetized beloware so familiar to even the humblest mathematician that mostreaders of this book need give them no more than a passingglance. But if you are one of those adventuresome souls forwhom most mathematics books are incomprehensible, but whofor some strange reason have decided to look into this one,  youmay find it worthwhile to go over this brief, informal glossarybefore reading further.