1 apple
one apple / an apple
2 cat
two cats
3 book
three books
4 dog
four dogs
5 egg
eggs
6 fish (irregular)
six fish
7 gorilla
seven gorillas
8 hat
eight hats
9 igloo
nine igloos
10 jet
ten jets
11 king
eleven kings
12 lion
twelve lions
13 mouse (irregular)
thirteen mice
14 nut
fourteen nuts
15 octopus
fifteen octopuses
16 panda
sixteen pandas
