[Tex2002ans]

Originally Posted by fabien.benoit.19

@Quoth, @Tex2002ans, @kvn57
I can provide an offline tts solution for free, if you help with beta testing. Are you interested?

Sure. Send me a PM.

Don't know if I'll be able to get time to test it out in-depth, but let me know more info.

Originally Posted by Jellby

Fullstop as in an abbreviation? That's wrong, units are symbols, and are written without fullstop (but there would be a fullstop if that's the end of a sentence, of course).

Originally Posted by Notjohn

The book I'm reading at the moment is from Cambridge University Press, by a German-educated Cambridge don.

From a quick look, Cambridge University Press's own Style Guide says this:

Measurements

Avoid leaving a space between number and unit of measurement (10km, not 10 km). Commonly used measurements include: cm, mm, km, g, l (litre), MB, GB, kHz, MHz, KB. Follow the International System of Units (SI) as a guide for units of measurement. If your source material uses imperial units, always include the metric equivalent in brackets.

but they are wrong.

SI Units should always be typeset with the space (non-breaking and/or thin).

(For more info on that, see "The International System of Units (SI)" standards (PDF).)

Non-breaking Spaces

"10 km" is considered a single chunk, so it would be awful if broken across lines such as:

The person ran 10
km home.

Typesetting with non-breaking spaces alleviates this problem.

Thin Spaces

The other issue is a normal space is "too large"—making "number + Units" look like 2 separate words—so a thin space between allows them to look like a single, cohesive whole:

• 10 km (space = Okay/Acceptable)
• 10 km (thin space = Best)
• 10km (no space = Wrong)

This typographical difference becomes much more apparent when working on documents with:

• many units
  
  • Including temperatures!
• equations/formulas
  
  • Especially inline!
• large (complicated) units
  
  • kg/K = "kilograms per kelvin"
    
  • m/s^2 = "meters per second squared"
    
  • kJ/kg·K = "kilojoules per kilogram per kelvin"
• + large (complicated) numbers
  
  • 1.0635kJ/kg·K (Wrong)
    
  • 1.0635 kJ/kg·K (Correct)
    
  • 1.0635 kJ/kg·K (Acceptable)
• lots of numerical data.

Across single sentences, it doesn't make much difference, but across entire paragraphs + books, it begins to add up.

Here's a random page I ripped out a Thermodynamics book I worked on:

Thin Space vs. No Space vs. Full Space



- - -

Side Note: This example was just what I had on hand + whipped up quickly.

Of course, this bad-spacing-between-units issue would look much worse in Word/ebooks. (LaTeX does a good job hiding it.)

- - -

(Inline) Equation Spacing

Similar typesetting needs to be taken account with Maths formulas too.

Take the equation "x MINUS y EQUALS negative three z":

• x-y=-3z (No Italics = Wrong)
• x-y=-3z (Hyphens = Wrong)
• x−y=−3z (Minus Signs = Better)
• x − y = −3z (+Spacing = Best)

Again, the entire equation is "a single chunk", so:

• shouldn't be broken across lines (if possible).
  
  • If there is a linebreak, then it can only be allowed before certain symbols (+, −, =, ...)
• Mathematical spacing rules apply.

Here's the sample page above...

Without unit+equation spacing vs. the final "thin spaced" book:



Especially see "S1" and "S2" in the lower paragraph (GIF comparison):



See the readability difference? Now times that by hundreds of pages.

Originally Posted by Notjohn

That's the way I would write it, though with a full stop, but British books, especially from academic presses, often omit the space (and the full stop of course). The book I'm reading at the moment is from Cambridge University Press, by a German-educated Cambridge don.

I think this is similar to the editor's (wrong) rule of "get rid of all double spaces".

That rule was morphed and applied because of decades of typographically-inferior technology:

• typewriter
  
  • Only had a single type of space.
• early computers / word processing programs
• bad/piss-poor hyphenation/justification algorithms

but there's no need to keep forcing that "single space rule" when we have much better tech now.

Cambridge's editors probably got sick of Word (and similar programs):

• breaking units across lines
• adding huge (and inconsistent) gaps
  
  • Bad justification!

so they decided to go full-insane and combine the numbers+units together...... instead of selectively applying non-breaking spaces.

- - -

Side Note: See my related discussion about non-breaking spaces between initials+last names:

• 2021: "RegEx: Insert nbs between initials, etc."
  
  • Antidote can detect+insert non-breaking (or thin) spaces between:
    
    • Units
      
    • Initials
      
    • Punctuation (French)
      
    • (+ many other cases)
      
  • LanguageTool can detect+add a space between:
    
    • Units
      
    • (Is aware of other cases. May be added some time in the future.)
      

And see the double-spacing discussion way back in:

• 2019: /r/writing: "O vs 0"
• 2019: /r/writing: "I finally finished my first novel. Here is my process, and lessons learned."
• 2014: "[old thread] non breaking spaces (* and *) automatically removed"