# Is the expression "When the temperature is less than 15℃ and not less than 10℃...." is unnatural?

One of the English textbooks I have says as follows:

"2 ≤" can be written: "greater than or equal to 2", "not less than 2", "2 or more"

"≤ 5" can be written: "less than or equal to 5", "not more than 5", "5 or less"

The book also says that in the case of "2 ≤ X ≤ 5", it is not appropriate to combine these expressions because such combinations are unwieldy and unnatural in English, and that "2 ≤ X ≤ 5" should be written as 2-5 (inclusive).

I would like to know whether my example written in the Title" When the temperature is less than 15℃ and not less than 10℃, ..." is unnatural.

We would probably be more likely to say "between" but I've certainly heard versions of your sentence. One exception, though... instead of "and" use "but".

When the temperature is less than 15 C but not less than 10 C.

I've seen versions of this used quite frequently. Note, however, that the temperature range here is 14 C to 10 C. "Less than" 15 C is not inclusive of 15 C.

• I would say the temperature range is 10°C to 14.9999..°C or as some might write, [10,15[. Because temperature is a continuous variable and because it seems more natural to give the range from minimum to maximum than in the reverse. Jun 14, 2017 at 18:51
• @Spehro Pefhany: from 10.00 to 15.00 is how you might write it if you wanted the reader to know that 15.01 would be invalid and that a difference of only one hundredth is significant. You should choose the number of decimal points to reflect the relevant precision. Absence of numbers to the right of the decimal points implies acceptance that the measuring device is not super precise (and does not need to be).
– TimR
Jun 14, 2017 at 19:19
• @Tᴚoɯɐuo So do you think the 14 is okay? It does not seem right to me. Partly because 1°C is significant in terms of human perception. Jun 14, 2017 at 19:28
• @Spehro Pefhany: If the temperature needs to be between 10 and 15 inclusive (not less than 10 and not more than 15), it would be "from 10 to 15". We don't need to assume that this has to do with human perception. We could be talking about a device.
– TimR
Jun 14, 2017 at 19:30
• @SpehroPefhany I intentionally left the order the same as the question order... it is not an example of how to say it, all I'm doing is emphasizing that 15 C is not included in the statement "less than 15 C...". If you want to be pedantic about minute fractions of a degree, go right ahead but I don't really see the benefit as that's not what the question is about. Jun 14, 2017 at 20:26