Is it acceptable to have the following sentences in formal writing?

2.5 years have already been completed.


n shows the number of something.


Contrary to the other answers, I see no reason not to use the forms shown.

If Abraham Lincoln could say:

"Four score and seven years ago, ..."

... and I can say ...

"15 cars overtook me on the way to work today"

then you can say:

"2.5 years is ..."

Some publications use the convention that single digit numbers are written in full ("One") while larger numbers are written as numberals ("100","15,234").

Likewise, a variable is effectively a noun, and can be used to begin a sentence.

i represents the iteration number.

There is a problem here with capitalisation. Do you capitalise the i to comply with normal English writing conventions? Do you leave the i lower case, because the upper case version would not work in your case-sensitive programming language?

That's a matter of house style. I would personally not capitalise it. Avoiding the issue by always phrasing the sentence differently is a valid strategy.

The variable i represents the iteration number.

The iteration number is represented by i.

  • 1
    If you write out the number in letters, then of course it is fine. Feb 14 '12 at 0:24
  • Similarly in sentences like “π is the ratio of a circle’s circumference to its diameter.” or “ℯ is the base of the natural logarithms.” Certain words are not allowed to capitalize, like iPhone. Bringhurst doesn’t think too much of such nonsense, but the meaning of such things in mathematics (and hence programming) is well-established. “e = mc² changed the world” looks perfectly fine. One could also write that in Unicode as “𝑒 = 𝑚𝑐² changed the world.” Similarly, one could write “𝜋 is transcendental.” It would be absolutely wrong to capitalize any of those.
    – tchrist
    Feb 14 '12 at 16:28
  • In principle, I agree that there's nothing wrong with starting a sentence with a mathematical symbol, as long as there's no danger of confusing the reader. In practice, I fear that such sentences will provoke editors, so I tend not to write them. Dec 6 '13 at 3:08
  • @tchrist, I agree with your point, but what an odd example to use, writing E = mc² with a lowercase e.
    – SU3
    Mar 30 at 21:06

It is generally not recommended in formal prose, because it makes it harder to see where a new sentence begins, as dots are also used for abbreviations. In a technical manual or academic article, I would try to avoid it as well. A new line may provide extenuating circumstances for numbers, though probably not for variables.


No it is not.

In 4th grade I was taking exam to be accepted in Math High School (one of top 3 in our country). I had to solve some sort of a puzzle problem - deduce what numbers correspond to letters in an equation. It was some sort of a rebus.

My proof was immaculate, but they deducted half of the marks for something like:

"Because of the above conclusions in the equation for A stays 7.6 is the corresponding number for the letter B because ...".

They had read it as 7 times 6.

The alignments and the formats of different types of formal texts have its own rules with the general purpose of allowing the people concerned to read it and to understand it better. So it is not a good idea.

  • That was a not understandable example. Can you perhaps format it to show where you start the sentence?
    – mplungjan
    Feb 13 '12 at 10:14
  • 3
    There is a sentence that begins at the first 6. Sorry, but I found it perfectly understandable, and a great illustration.
    – user16269
    Feb 13 '12 at 10:25
  • I have edited your answer in an attempt to make it readable English, and getting the meaning out. Let me know if I've got anything wrong.
    – slim
    Feb 13 '12 at 11:02
  • 3
    If I've understood the issue here, it is that you failed to put a space after the "7." so the examiner didn't realise that the 6 begins a new sentence. Surely the solution here is to use spaces correctly, not to avoid the sentence structure altogether.
    – slim
    Feb 13 '12 at 11:03
  • @slim: Examiners will not see as examiners - they see as the typical reader, to evaluate the writing. I'm sure they can understand fine, so "didn't realise" is not a possibility but a necessity.
    – Kris
    Feb 13 '12 at 11:15

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