Minus or Negative?

There are a lot of misconceptions around negative numbers (see this post) and I sometimes wonder if this is down to confusion caused by the language we use when describing a number that is below zero. I know some maths teachers interchange between calling something negative or minus depending on the situation or the mood they are in. Outside of the maths classroom, the word “minus” is used frequently and almost always when describing temperature. Is it correct though?

I put a poll on Twitter to try and find out what other maths teachers think and the results were surprising for me. More than half of the teachers, it seems, have a different view to me..

I know that I can be a bit pedantic but I argue that we should always use the word “negative” when we are describing a number below zero. For me it is a case of opposites. When talking about operations, the opposite of “add” is “subtract”. When talking about the operators themselves, then the opposite of “plus” is “minus”. So when talking about the property of a number, then the opposite of “positive” has to be “negative”.

So why does it matter? I find that there are many barriers to understanding the fundamentals of mathematics that stem from the language we use. An example is the fact that we say “half”, “third” and “quarter” rather that “twoth”, “threeth” and “fourth”  when talking about fractions (all the other unit fractions seem to follow a more intuitive logic). I’m not sure if other languages have similar barriers so would love for anyone to let me know..

Anyway, when it comes to negative numbers, I have found that even some of the best mathematicians I’ve taught get themselves into a pickle with unhelpful phrases such as “two minuses make a plus” and struggle with the misconceptions this brings. It is much more useful, in my experience, to be able to separate the language and always use the words “positive” and “negative” to highlight a property that belongs to a number and add/plus or subtract/minus as an operation that we apply to a number. Being clear and consistent with the language removes this barrier and allows students to concentrate on getting to grips with the conceptual understanding.

Do you agree/disagree? Have you been convinced? Please comment below to let me know..

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19 thoughts on “Minus or Negative?

  1. Permalink  ⋅ Reply

    jemmaths

    January 26, 2017 at 6:33pm

    I like to interchange them, so that my students become familiar and happy with both words, simply because they will encounter both throughout their lives. Having said that, I do explain that I will use both, and why. I sometimes say things like “negative, or minus, 5” to build familiarity with them as synonyms. I also expose them to negatives written with and without brackets around, so that they don’t get thrown if they see them presented in the way they haven’t been taught.

    • Permalink  ⋅ Reply

      MathedUp

      January 26, 2017 at 8:57pm

      I completely agree that they need to have an awareness of both. I guess my point is that I want them to have clarity in their thinking when calculating with them and I would prefer their internal voice to say “negative” rather than “minus”.. I like the fact that you expose them to multiple written forms – I don’t think I do that enough!

      • Permalink  ⋅ Reply

        jemmaths

        January 26, 2017 at 9:47pm

        I can totally see the arguments for choosing one way and sticking with it for lots of areas of maths. This is one where I choose to go both ways!

  2. Permalink  ⋅ Reply

    Chris Hawkins

    January 26, 2017 at 11:47pm

    I would posit that ‘plus’ is used as a descriptive word, particularly in relation to temperature (and particularly in relation to low positive temperatures), possibly because ‘minus’ is used as a descriptive, and therefore ‘plus’ is the logical opposite. For example “last night it was minus two degrees, but today it rose to plus three degrees”.

    • Permalink  ⋅ Reply

      MathedUp

      January 27, 2017 at 12:00am

      I had never thought of that before..

  3. Permalink  ⋅ Reply

    Jenny B

    January 27, 2017 at 8:19pm

    I’m trying hard with my negatives 🙂

    • Permalink  ⋅ Reply

      MathedUp

      January 28, 2017 at 11:01pm

      I know you are!!

  4. Permalink  ⋅ Reply

    phil

    January 31, 2017 at 12:56pm

    I like the word take for subtract – quick to say and obvious inverse of add

    • Permalink  ⋅ Reply

      MathedUp

      February 20, 2017 at 8:35pm

      I like it too!

  5. Permalink  ⋅ Reply

    Nick Edwards

    February 7, 2017 at 1:14am

    I am quite adamant about the use of ‘negative’ over ‘minus’ if describing a number less than zero. ‘Negative’ is an adjective – describing the property of the number. ‘Minus’ is a verb ‘to take something away’. So if I see the following in a lesson 4 – -3 I would always teach my students to read it as ‘4 minus negative 3′ (though to be honest, I actually very rarely use minus at all – I’d normally say 4 subtract negative 3’.

    • Permalink  ⋅ Reply

      MathedUp

      February 20, 2017 at 8:37pm

      I agree. I’m not very consistent with the word I use for “subtract”..

  6. Permalink  ⋅ Reply

    teachingbattleground

    February 15, 2017 at 12:08pm

    “Negative five” is unambiguous. “minus five” could mean “negative five” or it could mean “subtract five”.

    • Permalink  ⋅ Reply

      MathedUp

      February 20, 2017 at 8:44pm

      Absolutely. I recently realised there is an exception in my language.. For example, when solving x^2 = 16
      I would say the solution is “plus or minus four”..

  7. Permalink  ⋅ Reply

    Matt Rosenberg

    March 20, 2017 at 12:52pm

    I find it’s best to mix them up, not only for real life resilience but also because they are essentially the same thing. 3x*-2 = -6x “Three x multiplied by negative two equals negative 6x” but 3x(y – 2) = 3xy – 6x, here you need to do the same calculation when you expand the bracket but you are much more likely to read the second term as “minus six x” or “subtract six x” because of the first term.

  8. Permalink  ⋅ Reply

    arkalot

    April 2, 2017 at 2:10pm

    This is all fine but there is a problem, which is why I interchange minus/negative all over the place

    Consider: 20 – 10 + 4

    So you say: twenty minus ten plus four

    no problem you think

    now use BIDMAS/BODMAS

    the tendency is to do 10 + 4 = 14 then 20 – 14 = 6 but this is not the correct answer!

    You need to do -10 + 4

    So is it negative 10 or minus 10? (thats why I tell kids to work L – R for +/- only questions)

    • Permalink  ⋅ Reply

      MathedUp

      April 10, 2017 at 8:06pm

      A better solution would be to not use BIDMAS 🙂

      • Permalink  ⋅ Reply

        arkalot

        April 27, 2017 at 11:47am

        Maybe – but still may arise as part of a BIDMAS question 🙂

        2 x 5 – 20/2 + 2 x 2

  9. Permalink  ⋅ Reply

    Oliver Gray

    May 15, 2017 at 3:08pm

    I think it’s a really important distinction to make, and try to emphasise it by writing the negative sign as a superscript proceding the digit, wheras I write the minus sign in the usual place. I think we as mathematicians ought to separate our objects from our processes, our nouns from our verbs.

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