I'm reading a book and I saw there a sentence with the word "fold" but I am not sure about the meaning of this word in the context:

Overall, glia outnumber neurons in the mammalian brain 10-to 50-fold.

Does this "fold" mean like "times"?


Yes, it does. When something changes from 1 to 100, that's a hundredfold. 300 to 900 is threefold.

Generally, if a number is followed with -fold, it means [number]-times.

Hopes this helps.


No, it is not correct. Saying something is X-fold is saying it is 2^x times. Think "folding paper." How many parts do you have if you fols a piece of paper three times? The answer is 8. Thus 3-fold is 8-times.

I talk with scientists frequently who are writing studies who don't know the difference between the two words, so you find them used interchangeably. I always point it out when I review a study, but given a moment of analysis, I can normally tell what they really mean. Having said that, there is ZERO excuse for allowing this error to continue.

If X is 10, then a "3 times" increase makes the result 30, while a "3 fold" increase makes the result 80. The difference is not trivial. Quality control and editors should know the difference; obviously they do not.

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