In typography, a thin space is 1/6 of the size of a conventional space used in a Word doc to separate words, numbers, and other textual elements. They are used often in scientific manuscripts with mathematical equations and large numbers to make them easier to read. Peer-review journals also require authors to follow specific style and formatting guidelines, including using thin spaces. These guidelines are based on publishing conventions defined by various professional organizations, including the International System of Units, International Union of Pure and Applied Chemistry, the International Bureau of Weights and Measures, the AMA Manual of Style, The Chicago Manual of Style, Scientific Style and Format, and the APA Manual of Style, to name a few.
All of these organizations call for using a thin space in two common scenarios in scientific manuscripts: 1) as a delimiter to separate large numbers into groups of thousands and 2) to separate operators in math equations. For numbers accompanying a scientific unit (meters, seconds, moles, amperes, kilograms, kelvin, candela), the International System of Units calls for separating whole numbers above 999 with a thin space placed between the third and fourth place value to the left of the decimal point to mark the thousands place value. These numbers can be separated by a thin space into groups of three digits, as shown in examples below.
845 631 004
195 231 229
Note this pattern also holds for numbers expressed as decimals, as shown by these examples:
54.628 424 295
For numbers with only 4 place values, no thin space is required, and instead the digits are closed up, as in these examples. 1234
This convention of using thin spaces to separate numbers larger than 999 differs from the common practice in the United States of using a comma to delimit the thousands place in a number above 999 as in these examples.
Throughout the world, there are different conventions for separating groups of thousands. For example, in France, Brazil Germany, Italy, and Russia, instead of using a comma, a decimal point is typically inserted to separate the thousands place in a number above 999 as in these examples:
In these countries, instead of separating a whole number and decimal with a decimal point, a comma is used, as in the examples.
Yet unlike the conventions for presenting numbers followed in the US or in other countries, the International System of Units only recognizes a decimal point (period) as the acceptable punctuation mark to separate digits, and it is used to separate whole numbers from decimals, as in the examples: 13.2
Another common use of a thin space in a scientific manuscript is to separate mathematical operators (+, ÷, ±, ~, =, <, >, −, ×, ⋅, ∩, ∫, Π , Σ) and the numbers that precede or follow them, as in the examples below. Thin spaces in equations and in large numbers improves readability.
345 ÷ 8 =
347 + 325 =
46 × 95.76 =
Unfortunately, Microsoft Word does not include a thin space in its advanced symbols settings. You have two options for creating a thin space in Microsoft Word: 1.) Use a condensed space, which allows for customizing and creating an approximate thin space. 2.) Use Unicode for creating an exact thin space. For the first option, check out this brief YouTube video: https://www.youtube.com/watch?v=iXDjo41IWd8
For the second option, creating a thin space with Unicode involves placing the cursor in the position where you want the thin space to appear, and then press the option key followed by the number 2009. This should produce a thin space. If these directions do not work for you, please check out this video that explains in detail how to use Unicode: https://www.youtube.com/watch?v=ShOJYrZaMJU
You may also find this article helpful: https://word.tips.net/T001812_Creating_Thin_Spaces.html
One exception to these rules for using thin spaces with numbers is to respect style preference of journals that follow the conventions of the country where they are based. It is also more common that a journal does not use a thin space separating number when the content of a journal is nontechnical. Please let me know if you have any questions about using thin spaces. And subscribe to my blog for similar tips for writing scientific manuscripts: https://www.academicenglishsolutions.com/academicenglishsolutionsblog