Englishfor English speakers
online
Preposition
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If a system is online, it is connected (generally electronically) to a larger network.
I do a lot of shopping online, so I almost never have to leave the house.
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If a machine is online, it is turned on and is ready to do work.
Since the printer is back online, you should be able to again print from it.
contact
Noun
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When mathx/math makes or has contact with mathy/math, they touch each other physically.
The trains in Tokyo are so crowded that everyone has to stand in close contact to everyone else.
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By extension, its use as a metaphor:
He wore dark glasses so that he wouldn't have to make eye contact with anyone.
"Did you tell Chris about lunch today?" "No, I wasn't able to get in contact with him."
contact
Verb
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If A contacts B, A telephones B or writes a letter or e-mail to B.
If I can help further please do not hesitate to contact me at 012-345-6789.