Plain writing (aka, plain language and plain English) is simply another term for clear and concise writing, something writing instructors have been trying to instill in their students for literally centuries. Plain Writing has a number of definitions. One good one is: “A communication is in plain writing if its wording, structure, and design are so clear that the intended readers can readily find what they need, understand it, and use it.” But Albert Einstein—a plain writing master long before the term was coined—made a keen observation that applies to writing and just about every other human endeavor: “Any fool can make things bigger and more complex, but it takes a touch of genius to go in the other direction.”

Put one space after each sentence when using proportionally-spaced fonts, which means just about every font found on a computer including the one on this webpage (notice that an i takes up less than half the character-space width of an m). Put two spaces after sentences when using mono-spaced fonts, such as Courier New and those found on a typewriter. With mono-spaced fonts, an i takes up the exact same character-space width as an m. Reading documents written with mono-spaced fonts becomes, well, monotonous, so someone long ago decided to put two spaces at the end of each sentence to make it more readable and to act as an “eye rest.” It’s hard for some people to make this change because they’ve been putting two spaces at the end of a sentence forever. But if you need final proof of this rule, open any book, newspaper or magazine: you’ll find only one space at the end of each sentence.