# Elements of style. Writing an EE or IA in Maths, Physics, Bio, Chemistry or ESS, Part 3

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• Units

Write a space between the magnitude and the unit of a physical quantity, as in 150 cm, not 150cm.  The later means 150 times the speed of light times the mass.

One exception is the degree sign for angles.  So one writes 15° for the angle but 15 °C for the temperature. Also, observe that we have degrees celsuis, but not degrees kelvin.

Keep the magnitude and the unit on the same line (in Word one can force them to be as one word by using Ctrl-Shift-Space instead of just Space).

You don’t write the units in italics, else they might be read as variables.

If written as words, not as an abbreviation, units like newton, watt and joule are written in lower case. E.g. “The unit N, newton, is named after Isac Newton”.

When using units in the equation editor in Word, mark the unit, and then under start, format deselect italics.

I would also suggest you write, for example, 8 mm to 16 mm instead of 8-16 mm. The last could be mistaken for a subtraction.

• Variables

Variable names are usually written in italics, like x or v. Vectors are usually in boldface, x, v or as  ${\vec x}$ or ${\vec v}$  , and matrices are usually in uppercase non italic boldface like  X and V.  So called random variables are usually written in upper case italics like N or B.

The most important thing here is being consistent. It is very confusing to see a variable written as X in the beginning of a sentence then as x in the text and as x in a formula. In maths and natural sciences these would stand for different things. Since sentences should start with a capital letter, avoid  starting a sentence with a variable name, instead start with “The variable x stands for….” or something like that.

• Function names

Same thing here, be consistent. Don’t call a function F in one place and f in another. Don’t write the natural logarithm as Ln just because it is in the beginning of a sentence. The notation “Ln” is usually used for the multivalued complex logarithm, whilst “ln” usually stand for the principal branch of the natural logarithm. I.e, the logarithm we all have come to love (right?).  Don’t worry if you don’t fully understand what ” multivalued complex logarithm” and “principal branch” means. The important lesson here is that “Ln” and “ln” may mean different things, and that the languages of maths and physics are case sensitive.

Also, function names of predefined functions like cos and ln should not be in italics. When entering things like  sin θ in the equation editor, then you write sin, then you press space. This gives you a marked place to out your variable, and will make the text “sin” be in non italics. It should thus not look like this: sinθ. It sould be either sin θ or sin(θ).

Notable exceptions are functions with one letter names. They are, mostly, written in italics because they are, mostly, the names of variables too, or can be seen as that.   So we have for example f(x)=3x and y(t)=3t+2.

• Numbers

Numbers are usually not written in italics or in boldface, except possibly in headlines (boldface) or in captions (italics). In other words, you should, for example, write (a, 0) not (a, 0).
• Excel

If you use excel to make tables and your regional setting for the decimal marker is different from what you use in your work (usually a poin, “.”) then remember to replace say the decimal commas with decimal points before you copy the table into word. You do that by marking the table then use  the “Search and replace” function.

You might also change Excel to use decimal points as a standard.

• Graphs

Don´t forget to put useful labels on the axes. Also, if making a graph in excel, remove unnecessary things, like the symbol legend that may appear to the left of your graph. If you do some kind of curve fitting, remember to change the variable names to the variables you are actually using (that may not be x and y),  and then remember to change them to italics, as all the other variables in your text.

A better graph:

Graph 2: A scatter plot of the measurement of the length vs. the mass of a number of Anacondas, and a line of best fit for the given data,   The Coefficient of determination, R2  is also shown.

You may also add vertical lines, as I did. In excel you will find both this, and axis-labels under “Layout”.  If this is the result of some kind of measurement or survey, you should also add error bars to the points.

• Diagrams, figures, pictures, tables and graphs

You usually put a numbered caption on all  of those.  A figure is usually something descriptive that is drawn (by hand or using some kind of software). Diagrams, charts or maps are usually all called “Figure” in the caption.  A graph is something like the one above.  A picture is usually a photo or something painted. The caption is usually in italics and with a smaller font size than the running text, as in the caption of the figure above.
• Equations

Write longer equations, and important equations in separate lines, and indent them like

y=ax + bx + c

or as

y=ax + bx + c

You may also give them reference numbers, like

y=ax + bx + c                                (1)

You can then refer the equation by the number later on in the text. So equation (1) is thus referred to in this sentence.

You may also put the reference number before the equation like

(2)                 y=ax + bx + c

Equation may be but inline (in the lines of the text) like, y=ax + bx + c,but that is usually just for shorter equations that are just steppingstones in your work.

A suggestion is to not use high school maths or science  books as examples of how a maths or science text should look like. It does not look professional like maths text and articles usually do. Look instead at text as

https://www.math.wisc.edu/~angenent/Free-Lecture-Notes/free221.pdf

or why not

https://uu.diva-portal.org/smash/get/diva2:792672/FULLTEXT01.pdf

(I know, it is in Swedish, and the name is automatically generated by looking at the personal number…. but its still mine (^^,)).  The later is written using the type setting software LaTeX.

• Calculator notation…

…should not be used. I.e. you don’t use ÷ or *.  In text you may for multiplication use × or . . The former is found under “Insert” “Symbols”.

The . sign can be entered by using an ordinary point “.” but raised using the “x2” key under “Format”.

You can enter both, on a stationary PC,  by using an ALT sequence.  That means that you hold down the ALT key as you press a digit sequence. Hint: You may also copy and paste the symbols directly from this document!

ALT 0183 gives you ·

ALT 0215 gives you ×

ALT 0177 gives you ±

ALT 248 gives you °

Also, avoid the oridnary minus sign. Instead use the so called en-dash. You get this by

ALT 0150 that gives you –

Or, at least on a PC,  Ctrl and then the minus sign on the numeric keyboard might work. In Word you can also find it under “Insert”, “Symbols”, “More symbols”.

To see why you should use en-dash, compare -2 with –2.

In the equation editor you can find all these symbols, like × and ·,  under the design part. You can click on the arrow in the lower left corner of the Symbols tab to get more symbols.

Up a level : On writing an EE or IA in Maths, Physics, Bio, Chemistry or ESS
Previous page : Elements of style. Writing an EE or IA in Maths, Physics, Bio, Chemistry or ESS, Part 2Last modified: Nov 21, 2019 @ 22:07