obliged or obligated?
Obliged is how you feel and to do with morality (I am much obliged), while obligated is the legal meaning that says you are compelled to do something (You are obligated to operate under the correct safety procedures).
oblivious of or oblivious to?
Oblivious of.
obtuse or abstruse?
Obtuse is insensitive and abstruse is hard to comprehend.
Oceania or Australasia?
Australasia is commonly used for the area comprising Australia, New Zealand, Melanesia, Micronesia and Polynesia, though some people will insist on the more vague Oceania.
of
A lot of native speakers make the mistake of writing what they say: 'I should of come with you on holiday.' The intended word is have. In this instance, should've has become should of. They might sound the same, but using of instead of have in writing is sloppy.
oftentimes
An Americanism not yet used in British English, but is only a matter of time ...
OK or okay?
It is always preferable to write it OK, using capitals, and not 'okay'.
ongoing
'Talks, meanwhile, are ongoing,' is commonly heard on the news. Ongoing is a word that sticks in the throat of some, perhaps unfairly. It is a useful word that has a subtle difference in meaning from the suggested alternative continuing. 'Talks, meanwhile, are continuing' does not convey whether they taking place now, or whether they are scheduled. Ongoing is more immediate if talks, indeed, are going on.
onto or on to?
Two words please.
open access journal or open-access journal?
By itself, the noun is open access, with no hyphen. However, there must be a hyphen when these two words describe another noun, such as when writing open-access journal, open-access policy, open-access schedule, open-access technology etc.
or + acronyms
There is a tendency to take from speech the habit of using or to clarify an acronym, as in ‘The tour included an inspection of the LHC, or Large Hadron Collider, at CERN’. There is no need for ‘or’ in examples such as this.
or + range
It common enough, by try to avoid using 'The sales manage is away and won't be back for 5 or 10 days'. The intention here is to express 5 to 10 days.
no other
The line 'No other pain-relief tablet works faster' means the same without the word other in it. In 'No man will come between us, nor will any other man' you will have said so twice.
others behalf or others' behalf or other's behalf?
The important thing here is that you use the apostrophe. Use other's behalf when you are talking about separate individuals, and others' behalf when you instead mean a collective group.
outside or outside of?
In US English, outside of is by and large the accepted standard form, while in British English the only correct standard is to use plain old outside when expressing location of position.
The word outside automatically means 'outside of something' so there is no need to include 'of'. But, see all of.
over or overly?
Careful writers know that over is already a suitable enough and has the same meaning as overly.
over or more than?
When it comes to saying, 'The conference was attended by delegates from over 65 countries', the careful writer will always make sure to change 'over' to 'more than'. This keeps the true sense of the word 'over' to the meaning of being (physically) above something. 'We flew over the city in a balloon and we could see more than 60 km in every direction.'
overestimate or underestimate?
You would think that the meaning is clear enough for people to get this one right, but many get them confused. Take care to use the right one, especicially in a negative sense, such as in 'it is almost impossible to underestimate' – what does that even mean??
overstate or understate?
Like overestimate/underestimate, you would think that the meaning is clear enough for people to get this one right, but many get them confused. Take care to use the right one.
oxymoron
There is a tendency to use this as a synonym for 'contradiction'.
More specifically, an oxymoron is a more figurative contradiction of terms such as 'the living dead', 'fresh frozen' or ‘blinding vision’.
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.