Language

"An unitary" or "an union" or "an university" were used in the 18th century, but now "a" rather than "an" is standard when the initial sound is "yoo".

Naming convention

HTML math

Minus sign

Use [−1,1] instead of [-1,1]. The little hyphen is too short to be a minus sign.

TeX

Colon

instead of

Mapping arrows

When you want to define the domain and codomain of the mapping use

but when you define the actual mapping function use

Standard function names

Use

e^ix = cosx + isinx

instead of

e^ix = cosx + isinx

to prevent the function names from looking like a variable.

Imaginary unit

The imaginary unit i should not be confused with the common variable i. So to make the imaginary unit look different it is better to write

e^ix = cosx + isinx

than

e^ix = cosx + isinx

Embedded fractions

When a fraction is in a superscript or otherwise deeply embedded within some other notation, it is often more legible like this

than like this

Spacing

Integrals

Use

rather than

Sets defined by using braces

This is another place where small spacing adjustments make notation look better. This

is better than this

{f(x):0 < x < 2}