justified text

In more detail

Set a paragraph aligned left and its right edge comes out ragged: each line ends where its last word ended. Justified, every line but the last is brought out to the edge, and the room that was missing is shared out among the spaces of that one line.

So it is a measuring job before it is a drawing one. Each candidate line is measured in the very lettering that will draw it, at the size it will be drawn at, because a letter is not a fixed width: an i takes a third of the room an m takes.

What it does on a real document

A wide column takes it well. A narrow one — a table cell, a newspaper column, a note at the foot of an invoice — goes loose as soon as its words are long: the spaces stretch, channels of white run down the page, and the eye falls into them instead of reading.

The cures are small marks written inside the text itself: a place where a long word is allowed to break, with a hyphen appearing only on the line that actually breaks there, and a space that refuses to break so that an amount stays beside its currency. Neither shows in the finished document.

Where it comes from, and why

A compositor did this by hand, pushing thin brass and copper spaces between the words until the line filled its measure exactly, and resetting the line when it would not come out. The arithmetic has moved indoors; the job is the same one.

See it on a finished document

Breaking a paragraph up, and aligning it Soft hyphens and no-break spaces