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I was wondering if figure, number, digit and other similar words can be used exchangeably in mathematics?

What are the differences in their usage?

How about in other context, such as in computer science, and in life?

Thanks and regards!

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Number and digit cannot be used interchangeably; in ordinary decimal notation, there only ten digits, but infinitely many numbers. "Figure" usually refers to geometric figures rather than numbers; so, no. As for what happens in CS and in life, those are outside the scope of this site. – Arturo Magidin May 2 '11 at 2:43
@Arturo, "figure" often refers to numbers, as in "I added up this column of figures $5$ times - and here are the $5$ answers I got." But as "number" can't refer to geometric figures, the two words are certainly not always interchangeable. – Gerry Myerson May 2 '11 at 2:49
@Gerry: Thanks; I am aware of the use of "figure" for number, but it seems to be becoming more uncommon these days in ordinary language, and in my experience it is extremely rare of "in mathematics". – Arturo Magidin May 2 '11 at 2:53
@Gerry: I only compare their similar meanings. My questions might seem stupid, but it took me a while to realize "figure" means number not graph when reading some math related material found from internet. So I was wondering if such usage is acceptable. @Arturo: Nice to know your experience. – Tim May 2 '11 at 2:54
@Arturo: Well, there is the expression "significant figures". :) – J. M. May 2 '11 at 3:09

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