20Nxx Other generalizations of groups

• 20N02 Sets with a single binary operation (groupoids)
• 20N05 Loops, quasigroups, See also {05Bxx}
• 20N07 Mappings of loops
• 20N10 Ternary systems (heaps, semiheaps, heapoids, etc.)
• 20N15 $n$-ary systems
• 20N20 Hypergroups
• 20N25 Fuzzy groups, See also {04A72}
• 20N99 None of the above but in this section