The word space has exactly one purpose: to create horizontal clearance between two words. Likewise, the space bar has exactly one purpose: to insert a single word space.
Don’t use the space bar as a general-purpose white-space dispenser by holding it down and watching the cursor glide across the screen. Though a calming sight, it leads to anguish when formatting the document. Use exactly one word space at a time.
HTML supports a character called a
) which is roughly half the width of a word space. A thin space can be useful in situations where a standard word space seems too large, for instance after the periods in
W. A. Dwiggins.
If you thought that was the limit of word-space geekery, think again. Professional page-layout programs have even more choices. Adobe InDesign, for instance, supports the thin space, but also the third space, quarter space, sixth space, flush space, hair space, figure space, and punctuation space.
“Ifyou approve of smaller word spaces in some situations, why do you insist on only one space between sentences, where a larger gap might be useful?” Because you’re already getting a larger gap. A sentence-ending word space typically appears next to a period. A period is mostly white space. So visually, the space at the end of a sentence already appears larger than a single word space. No need to add another.