Plural

singular + -s

singular	plural
a car	two cars
a cassette	two cassettes
a lamp	two lamps
a hat	two hats
a cup	two cups

(after sibilants + -es)

singular	plural
a box	two boxes
a sandwich	two sandwiches
a suitcase	two suitcases
a rose	two roses
a garage	two garages

y after consonant is changed into -ies:

singular	plural
a city	two cities
a lady	two ladies
ABER: -y nach Vokal bleibt!!!
a boy	two boys

nouns on -f or -fe mostly form the plural on -ves:

singular	plural
a thief	two thieves
a wife	two wives
a roof	two roofs

nouns on o: + -es
(not: radio, video, disco, video)

singular	plural
a tomato	two tomatoes
a photo	two photos

irregular plural forms

singular	plural
a man	two men
a woman	two women
a child	two children
a mouse	two mice
a tooth	two teeth
a goose	two geese
a foot	two feet
an ox	two oxen
a (gold)fish	two (gold)fish
a sheep	two sheep