The plural of most nouns are formed by adding s.
The letter q is always followed by u.
Final e is dropped before a suffix beginning with a vowel,
but is kept before a suffix beginning with a consonant.
Final y, if preceded by a consonant, is changed to i.
When y is preceded by a vowel, the y is kept before any suffix.
The letter i comes before e except after c
or when sounded like a as in neighbor or weigh.

We’ll begin with a box and the plural is boxes.
But the plural of ox should be oxen, not oxes.
Then one fowl is a goose but two are called geese.
Yet the plural of mouse should never be meese.
You may find a lone mouse or a whole set of mice,
Yet the plural of house is houses not hice.
If the plural of man is always called men,
Why shouldn’t the plural of pan be called pen'

If I speak of a foot and you show me your feet,
And I give you a boot, would a pair be called beet'
If one is a tooth and whole set are teeth,
Why should not the plural of booth be called beeth'
Then one may be that, and three would be those,
Yet had in the plural wouldn’t be hose.
And the plural of cat is cats and not cose.

We speak of a brother and also of brethren.
But though we say Mother, we never say Methren.
Then the masculine pronouns are he, his and him,
But imagine the feminine she, shis, and shim.
So English, I fancy you all will agree,
Is the funniest language you ever did see.

Source unknown