An overtime or a overtime?^_^

Neither Soochu.
'Overtime' is an uncountable noun, so we would say some/a lot of/a little/etc. overtime.
P.S. If it WERE countable we would say 'an' because overtime begins with a vowel.
Cheers

I worked 3 hours overtime. ( The ' overtime ' here is ' adverb ' ) to mean how you work.

water is uncountable noun, that's why we say 2 litres of water not 2 litres waters

but waters with s means the ocean on the shore of a country.

eg. A pirate ship has encroached the waters of Thailand.


To know if a noun is countable or uncountable, you have no choice but to rely on Dictionary.

You're counting litres there, dude, not waters. All that that proves is that LITRE is countable.

Figuring out if something is countable or not is easy. Just fit the word into the blank spaces in the following. If what you end up with makes sense, the word is countable, otherwise it isn't:

One _____, two _____s, three _____s, four _____s, etc.

(That's a plural form after two, three and four).

BUT....

Contrary to what most people will tell you, *ANY* noun can, in theory at least, be used either countably or continuously. Water may be officially uncountable, but I can still sit down at a restaurant and order "Two beers, three cokes and two waters". Humans may be countable, but I can still say There is some human in you after all". It's not that there's no clear division, it's that there's no division at all. There is a default for most things (fruit=continuous, veg=countable)*, but you can override the default by how you use the word in a sentence.

Rommie

* whoever thought that up should be shot.

Hi,

THANK YOU.

Can you expand, if possible, on your explanation that there is a defualt for most things but you can override the default by how you use the word in a sentence.