Sick vs Ill
♥Ill is often used to mean ‘unwell‘ in British English. In American English ill is unusual except in a formal style. Note that we use ill after a verb.
She is ill.
♥In Attributive position (before a noun), many British people prefer to use sick. Sick is also the normal informal American word for unwell.
The President is sick.
♥Be sick can mean ‘vomit‘.
I was ___ three times during the night
The problems faced by mentally ___people need to be dealt with
She is never sea-__
His mother is seriously ___ in hospital
Toothache vs A Toothache
♥ Illnesses are usually uncountable in English, including those ending in -s : measles, flu…
But some more common minor ailments such as: a cold, a headache, a sore throat, a nose bleed, a cough, a rash… are countable, ie, they take the indefinite article (a,an)
♥While in British English, toothache, earache, stomach-ache and backache are uncountable. ( I have earache) in American English , they are generally countable if they refer to particular attacks of pain.
Compare:
I have toothache (BrE) // I have a toothache (Am E)
(Source Practical English Usage – Micheal Swan)
Ache vs Hurt
♥ What ‘s the difference between My leg hurts and My leg aches?
If your leg aches you have a continuous, dull (not intense) pain.
If your leg hurts, it is often stronger and sudden. Ex. Ouch! My leg hurts!
♥On the other hand, ache is used both as a noun and as a verb whereas hurt is only used as a noun.
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