There are a certain number of words where the spelling varies according to the part of speech, that is whether the word is a noun, a verb or, sometimes, an adjective. The commonest ones involve c in the noun and s in the verb.
In American English, s is commonly used for both noun and verb. American spelling also sometimes uses s where British spelling uses c.
Other commonly confused pairs:
You must choose which channel to watch.
He chose me the last time.
He's afraid they'll lose tomorrow.
That screw's a bit loose.
She's dependent on her parents.
She has an independent spirit.
The tax form asks for the number of dependants.
It's a matter of principle.
The principal star is the sun.
(But the Principal of the College, short for Principal Officer).
There are pens in the stationery cupboard.
The train was stationary at Platform 6.
And don't forget...
Complete the sentences below by tapping a word and then tapping the gap where the word belongs.
You'll never play the bassoon well if you don't .
He was afraid of his driving after the accident.
I'm opposed to such barbaric on .
Is that house over ?
My lawyer's was to the second option.