Oral

Oral = (1) using speech rather than writing: Always go for a written agreement in business than relying on an oral agreement.In the oral examination, she was asked to recite the name of all presidents. (2) of or relating to mouth: He has undergone an oral surgery.She practices good oral hygiene by brushing her teeth at least twice a day.

Both the words Spoken and Oral can be used to refer to language skills and the communication of information. However, oral is slightly more technical than spoken. The use of oral to mean spoken is restricted to certain technical phrases used in education: Oral skills, An oral examination.

Opposite

Use opposite and the opposite of only when you mean that two things are altogether different in nature, quality, or significance: thought that the medicine would make him sleepy, but it had the opposite effect.The opposite of long is short.The two men went off in opposite directions. (= one went to the left and one to the right)

To describe people opinions, life styles, ways of thinking etc., the usual word is different: These two schools of thought are completely different.

One thing is opposite another thing (WITHOUT to/of): The nearest bus stop is opposite the bank.

When opposite means facing the speaker or the person/place being talked about,it comes immediately after the noun: The house opposite is also for sale.

Operate

Operate = (1) direct or control something: Do you know how to operate this machinery? (2) perform surgery on (medicine): Have you heard what happened to the last patient he operated on? (3) to perform a function or work: The motor operates smoothly.The camera also operates underwater. (4) to be involved in military activities: A militant group  is operating against the government.

Operation = (1) the state of being in  effect or being operative: That law is no longer in operation. (2) a planned activity involving many people performing various actions: They planned a rescue operation. (3) a medical  procedure involving an incision with instruments: My mother is having an operation tomorrow. Mr. Barrett is going to have an operation on his back.

Once

Once = (1) one time only: You have to take this medicine once a day. (2) whenever; as soon as: Once it stops raining, we can go out. (3) at some indefinite time in the past: She was a very popular actress once. (4) used in negative sentences and questions, and after if to mean ever or at all: He didn’t once thank me.If she once decides to do something, it becomes difficult to change her mind.

Often

Often = (1) many times; frequently or in great quantities: The trains are often late.They often go out to dinner. (2) in many cases or instances: People are often afraid of things they don’t understand.

Every so often = sometimes; occasionally: I meet him at the club every so often.Every so often I heard a strange noise outside.

As often as not = quite frequently; usually; in a way that is typical of somebody/something: As often as not, he’s late for work.

Offence

Offence= (1) a feeling of anger caused by being offended: ‘He took offence at my slightest criticism.’ (2) the team that has the ball (or puck) and is trying to score: ‘Our team has the best offence in the league.’ Commit an offence (NOT do): ‘He is accused of committing various minor offences.’

O’clock

O’clock is a contraction of “of the clock” or “on the clock” that means “according to the clock”: ‘We are expected to be there at seven o’ clock in the morning.’

Do not use o’clock for times that include minutes or parts of an hour. Compare: ‘It’s four o’clock.’ ‘It’s ten past four.’

Use EITHER o’clock OR a.m./p.m. in a sentence (NOT both). Compare: ‘The work should be completed by seven o’clock.’ ‘The work should be completed by seven p.m.’

Do not use o’clock after 6.00, 7.00 etc. Compare: ‘8 a.m.’, ‘8.00’, ‘8.00 a.m.’, ‘8 o’clock’.

Island

Island = the island/isle of + name: ‘The holiday resort island of Langkawi’, ‘The Isle of Skye’. ‘I was on holiday with my parents on the island of Capri.’

When island means ‘a mass of land surrounded by water’, or is part of a name, the usual preposition is on (NOT in): ‘The prisoners were left on a small island with neither food nor drinking water.’

When an island is considered in terms of its people, tradition, and economy etc., both in or on are used: ‘No serious outbreak of cholera has been reported in the island for over twenty years.’

Imitate

Imitate = do something in exactly the same way that someone else does it: ‘Have you heard him trying to imitate an Englishman speaking French?’ ‘He walks as if he is trying to imitate Donald Duck.’

Copy = do the same thing as someone else: ‘As soon as I began cycling to work, people started copying me.’ ‘His little sister wants to copy him all the time.’

However

Unlike but, however is an adverb (NOT a conjunction) and is used only in formal styles: ‘I was hoping to deal with this matter quickly. However, the situation is more complicated than I thought.’ ‘The newspapers always carried stories of new advances and glorious victories. In reality, however, the war was not going well.’