Originate = (1) come into existence; take on form or shape: ‘The practice of Sati originated during ancient Ages.’ (2) to give rise to; initiate: ‘The policy was originated by the previous administration.’ (3) to create something new: ‘Darwin originated the theory of evolution.’

Originate is used in connection with things, ideas, customs etc. (NOT people): ‘No one really knows how the solar system originated.’

If you are born in and/or grow up in a particular place, town, country etc., you come from that place: ‘Where does Agneta come from- Sweden or Norway?’

Words that enter a language from other languages come from (or are derived from) those languages: ‘The name ‘terrier’ comes from the Latin word ‘terra’ meaning ‘the earth’.’

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’.

Use opposite and the opposite of only when you mean that two things are altogether different in nature, quality, or significance: ‘I 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’s 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 = (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 = (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.’