Englishfor English speakers
now
Preposition
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You use now when you want to say that something is true at this time. It is also used for things a short time in the future or a short time in the past.
I had many problems before, but I'm OK now.
What did you say just now?
The English teacher is at the library now.
—
You use now at the beginning of a sentence to get people's attention.
Now, I'd like to hear from other people too.
therefore
Adverb
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You use therefore to show that something was as a result of what was previously stated.
He was sick with the flu and, therefore, did not come.
Of course, words can mean different things. It is important therefore to understand, first, the meaning behind the words.