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’.

Media

Media= (1) the mass communication industry, esp. newspaper, television and radio; journalists and other related professionals collectively. (2) plural form of medium. So when you are talking about television, radio, and newspaper, use medium for singular reference: ‘Television is an important medium of infotainment.’

Use media (WITHOUT – s) for plural and group reference: ‘The mass media’, ‘The print media’.

The media usually takes a plural verb, especially in formal styles: ‘The media have shown considerable interest in the trail.’ A singular verb is sometimes heard in everyday conversation, but some careful users consider this to be incorrect.’

Matter

Matter= (1) a subject, situation or event under consideration: ‘It is a matter for the police.’ (2) used to mean ‘problem’ or trouble’ only in questions and negative sentences: ‘What is the matter?’ ‘There’s nothing the matter.’

It doesn’t matter + clause: ‘It doesn’t matter if you can’t answer all the questions. Just do your best.’

Subject + doesn’t matter: ‘The results don’t matter. Just do your best.’

Nothing/something is the matter or there is nothing/something the matter: ‘I think there’s something the matter with the central heating. It’s cold here.’ ‘Don’t worry. Nothing’s the matter. It’s just a tiny cut.’

Marriage

Marriage = the act of marrying; the nuptial ceremony of becoming husband and wife considered from a purely religious or legal point of view: ‘Her parents are against the marriage.’

Wedding = the social event at which the ceremony of marriage is performed; the occasion when this ceremony takes place and the celebration that follows it: ‘I never see most of my relatives apart from at weddings.’

Married = be/get married to sb (NOT with): ‘How long has she been married to him?’

Mainly

Mainly= for the most part; chiefly; primarily; to the greatest extent: ‘This movie is mainly about the pros and cons of reservation policy.’

To show that one particular feature or item is more important than all others use above all: ‘The person we’re looking for has got to be smart, intelligent, and above all trustworthy.’ ‘Above all, the government wants to avoid an increase in inflation.’