The answer is of course fish, as in
trough
women
options
Then I was reminded of a poem that you may or may not know that shows some of the peculiarities of the English language... I googled and found it
Quote by "]
English is Easy!
We'll begin with box, and the plural is boxes;
But the plural of ox should be oxen, not oxes.
Then one fowl is goose, but two are called geese,
Yet the plural of moose should never be meese.
You may find a lone mouse or a whole lot of mice,
But the plural of house is houses, not hice.
If the plural of man is always called men,
When couldn't the plural of pan be called pen?
The cow in the plural may be cows or kine,
But the plural of vow is vows, not vine.
And I speak of a foot, and you show me your feet,
But I give a boot--would a pair be called beet?
If one is a tooth and a whole set are teeth,
Why shouldn't the plural of booth be called beeth?
If the singular is this and plural is these,
Why shouldn't the plural of kiss be called kese?
Then one may be that, and three may be those,
Yet the plural of hat would never be hose;
We speak of a brother, and also of brethren,
But though we say mother, we never say methren.
The masculine pronouns are he, his and him,
But imagine the feminine: she, shis and shim!
So our English, I think you will all agree,
Is the trickiest language you ever did see.
I take it you already know
Of tough and bough and cough and dough?
Others may stumble, but not you
On hiccough, thorough, slough, and through?
Well done! And now you wish, perhaps
To learn of less familiar traps?
Beware of heard, a dreadful word
That looks like beard and sounds like bird.
And dead; it's said like bed, not bead;
For goodness' sake, don't call it deed!
Watch out for meat and great and threat.
(They rhyme with suite and straight and debt.)
A moth is not a moth in mother,
Nor both in bother, broth in brother.
And here is not a match for there.
And dear and fear for bear and pear.
And then there's close and rose and lose--
Just look them up--and goose and choose.
And cork and work and card and ward,
And font and front and word and sword.
And do and go, then thwart and cart.
Come, come, I've hardly made a start.
A dreadful language? Why, man alive,
I'd learned to talk it when I was five,
And yet to write it, the more I tried,
I hadn't learned it at fifty-five!
Anyone know any more?
;)