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.
Oceana 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 or time...
OK or okay?
It is preferable to always write OK, using capitals.
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.
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’ when doing 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. No man will come between us, nor will any other man. You've said it twice now.
others behalf or others' behalf or other's behalf?
other's/others' 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.
our thoughts are with, out thoughts go out
...
outside of or outside?
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.
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’ or ‘blinding vision’.
