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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.2011-05-02
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    @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.2011-05-02
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    @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".2011-05-02
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    @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.2011-05-02
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    @Tim: As a sort of analogy, digits are to numbers, what letters are to words. As Arturo points out, there are 10 digits, an infinitely many numbers, just as there are only 26 letters (52 if you count capital letters, too) in the English language, but many, many more words. Actually, I found the same analogy here: a short video on the difference between numbers and digits: http://www.youtube.com/watch?v=vBFxMndAUgw2011-05-02
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    @Arturo: here is where I saw figure is used to mean number: 2nd line, page 2 of http://docs.google.com/viewer?a=v&q=cache:ip88a_Skz5AJ:www.richardclegg.org/networks2/Worksheet2_06.pdf+m/m/1/2+queueing&hl=en&gl=us&pid=bl&srcid=ADGEESgYkACpxXcr2NnfPe6faKIVHyhyOtG_uxhLG06RTUywSzCC-BFgZFNnlHF1O20C-s6rjr8mKVoqwXmgAAui18Y0yXpKt0a8pH97zOkrUhqxBzzfwdCqb_APrUG3mW-wwiExTbZP&sig=AHIEtbR4DyK2iB8UOO9OydDApkeP1QcFZQ "The final figure 2 means that at most two customers are allowed in the system".2011-05-02
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    @Arturo: Well, there is the expression "significant figures". :)2011-05-02
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    @J.M.: Where it is used in place of "digit", not "number". (-:2011-05-02
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    @Tim: You're right: there is ambiguity with respect to the distinction (number, digit, figure); I think we're just trying to point out some good ways to differentiate their uses. The English language, though, is often ambiguous, and so you need to take the context into consideration. "Figure" is used in math texts, as it is in your text on Google.docs, and many other places, to refer to a table, chart, graphic, drawing, data, demonstration, etc. How it's being used, and what it means, may need to be gleaned from the context. Also, would it help to think of digits as "numerals"?2011-05-02
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    Anyway, to make @Amy's statement more accurate: "there are 10 digits in the *decimal* number system". In binary, the only digits you have are 0 and 1, and similarly for other base-$b$ number systems.2011-05-02
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    @Amy: Thanks! I was more concerned about if using figure as number is proper in mathematics.2011-05-02

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