word-spacing controls the gap between words

That's a very short one. I was reading "CSS rules that will make your life easier" and came across word-spacing which I haven't seen before.

.foo {
  word-spacing: 3px;
}

The above can be used to definie the gap between words. I could imagine that this could be useful when dealing with custom fonts to make the switch from fallback font to custom font less jumpy. :)

You can find all needed info on MDN and before you jump right onto it please consider that this property could slow down reading speed of your users.