Which is correct?
The molecular weight of this substance ranges from
- two hundred to two hundred and sixty.
- two hundreds to two hundred and sixty.
I need to spell the numbers out for some reasons and I'm stuck. Thank you for your help!
There are two ways to use any number word in English.
The first is as a cardinal number. In this case, it's invariable. It doesn't show the plural.
A hundred and five cows.
Two thousand is more than I expected.
Forty million, seven hundred thousand and sixty-three accounts have been opened.
The second use is as a common noun, with the meaning "batch of N". This use is countable, and it does show the plural.
There are hundreds of people here.
→ There are several hundred people here.
Dozens of species go extinct every day.
→ Several dozen species go extinct every day.
We spend billions of dollars on national defence.
→ We spend several billion of dollars on national defence.
Even small numbers can be counted this way.
They left the building in twos and threes.
→They left the building in groups of two and in groups of three.
There are a few other quirks to how we use number words, but those are the broad strokes.