Life is but a dream ?
I'm trying to translate this phrase into Russian, but translators give me quite opposite meanings
1)Life is but a dream - life is not life but a fairytale (word-by-word translation) which in Russian means a happy life
2)Life is but a dream - Life is a dream (it's not real, it's just an illusion)
Which one is correct?

Question

Answer

The word 'but' is equivalent to 'just' or 'only'.  The phrase means "Life is just a dream".

You will come across this adverbial meaning of 'but' quite often in older and more formal contexts.  For example, if you see a film set in the 19th century, you might hear the phrase "He is but a child", meaning "He is just a child" (not an adult).

Either of your interpretations of 'dream' would be correct.

Answer

Maybe this'll help you? It has a couple of translations:
https://glosbe.com/en/ru/life%20is%20but%20a%20dream

And according to my short search you can feel free to interpret "dream" in any way you see fit (or find in a dictionary).
There is no limit of one particular meaning.

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