| Answer | Crossword Clue |
|---|---|
| singleton | A set that contains exactly one element |
| singletons | A set that contains exactly one element |
| proper | Denoting a subset or subgroup that does not constitute the entire set or group, esp. one that has more than one element |
| mappings | An operation that associates each element of a given set (the domain) with one or more elements of a second set (the range) |
| mapping | An operation that associates each element of a given set (the domain) with one or more elements of a second set (the range) |
| kernel | subset of the elements of one set (as a group) that a function (as a homomorphism) maps onto an identity element of another set |
