100s, 100's or hundreds?
First, there is no need for an apostrophe (') between the last 0 and the s, it's just 100s.
Now, even though you'll see 100s used a lot, keep it in mind that some people argue that it is better to use hundreds if that's what you mean. For one, it is more elegant to use words. For another, it has been pointed out that 100 means one hundred, not 'hundred'. So maybe it should be 00s for hundreds but that is plain silly.
From another point of view, using 100s does make sense, if for only practical reasons. 100 is also a hundred, as in "It'll cost you a hundred". Therefore, 100s is justifed as being multiples of hundreds, or 100s.
10:00 or 10.00?
When it comes to expressing times in writing, be aware that there are three common approaches. The first of these is to use the system of the 24-hr clock. Times are expressed as 23:00 for eleven p.m. The 24 hours of the day are expressed from 0 to 24. If you use this, make sure you use the colon : between the numbers.
The second system is to use the 0–12, 0–12 system. This is the standard form in the Australia, Canada, New Zealand, US, UK etc, where the 24-hour clock remains a confusing and unfamiliar system. So 10 o'clock at night is 10, not 22, in all the said countries. If you are producing written communication for these countries it is best to use the 12-hr clock.
The third aspect to be aware of is that the US uses a colon and the UK a full stop. So in the US it's 10:00 and in the UK it's 10.00.
The preferred choice is twenty-ten and the twenty-tens.
Overused and over here.
This page last updated: 15 November 2014
Jesse Karjalainen is the author of The Joy of English: 100 conversations about the English Language, Cannibal – the language and history of the discovery of the New World, and Roanoke – the language and history of Early Colonial America.