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How is the word ratio defined? I know of two different interpretations of the term ratio, and they are somewhat contradictory. They are:

1) The Reynolds number is the ratio of inertial force to viscous force. It may be defined $Re={Ul}/{\nu}$.

2) The dilution ratio is the ratio of cordial to water in a drink. For Robinson's it is 1:4, 1 part cordial and 4 parts water.

These measures are both ratios, but refer different measures. If the ratio is referred to but not defined, then it is not clear how to interpret it. Is there a good way to distinguish between these two kinds of ratios? I personally try to avoid the word ratio because of this potential confusion.

Chogg
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  • May be, for the second one, we could use $proportion$ ? – Claude Leibovici Jul 30 '14 at 10:49
  • Ratio is one thing divided by another. I fail to see how the two given uses are different. – Karolis Juodelė Jul 30 '14 at 10:56
  • @KarolisJuodelė The difference is that in 2) the ratio is between the different components, rather than of the total. One fifth of the drink is cordial, but the volume of cordial is one quarter of the volume of water.

    I'm clearer on the difference now. It is just a matter of being a ratio of the components or a proportion of the total. I think the language used in scientific literature is not always clear between these two cases though. Has nobody come across statements in scientific that are unclear in this way?

     – Chogg Aug 08 '14 at 19:15
  • Again, everything that is $a$ divided by $b$ can be called ratio. You restricted the word only to parts of something, but that is too narrow. For example, derivative is a (limit of a) ratio between $\Delta f(x)$ and $\Delta x$, where $f(x)$ and $x$ do not form any sort of "total" and may even be of different types. – Karolis Juodelė Aug 08 '14 at 19:29
  • The wikipedia page gives good colloquial examples of this http://en.wikipedia.org/wiki/Ratio#Fraction – Chogg Sep 03 '14 at 21:02

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