...2 people
1 child...
...2 children
1 foot...
...2 feet
...2 women
1 tooth...
...2 teeth
1 man...
1 focus...
1 fungus...
...2 fungi / funguses
1 fish...
...2 fish
1 alumnus...
...2 alumni
1 index...
...2 indices / indexes
1 mouse...
...2 mice
1 thesis...
...2 theses
1 sheep...
...2 sheep
1 goose...
...2 geese
...1 criterion
2 data...
...1 datum
1 matrix...
...2 matrices
2 dice...
2 bacteria...
...1 bacterium
1 cactus...
...2 cacti
1 louse...
...2 lice
1 ox...
...2 oxen
1 phenomenon...
...2 phenomena
1 crisis...