Jus­ti­fied text is spaced so the left and right sides of the text block both have a straight edge. The usual al­ter­na­tive to jus­ti­fied text is left-aligned text, which has an un­even right edge. Com­pared to left-aligned text, jus­ti­fi­ca­tion gives text a cleaner, more for­mal look.

Jus­ti­fi­ca­tion works by adding white space be­tween the words in each line so all the lines are the same length. This al­ters the ideal spac­ing of the font, but in para­graphs of rea­son­able width it’s usu­ally not distracting.

If you’re us­ing jus­ti­fied text, you must also turn on hy­phen­ation to pre­vent grue­somely large spaces be­tween words. I’ve been sur­prised at how many law­yers quib­ble with this ad­vice. On what grounds? “It’s just not how we do things.” I’m afraid there’s no room for de­bate on this point, as the con­se­quences are of­ten dire—

Jus­ti­fi­ca­tion is a mat­ter of per­sonal pref­er­ence. It is not a sig­ni­fier of pro­fes­sional ty­pog­ra­phy. For in­stance, most ma­jor U.S. news­pa­pers and mag­a­zines use a mix of jus­ti­fied and left-aligned text. Books, on the other hand, tend to be justified.

If I have to use a word proces­sor for a project, I al­most never jus­tify text. Why not? Jus­ti­fi­ca­tion is ac­tu­ally a rather so­phis­ti­cated math­e­mat­i­cal process. The jus­ti­fi­ca­tion en­gine in a word proces­sor is sim­plis­tic com­pared to that of a pro­fes­sional page-lay­out pro­gram. Word-proces­sor jus­ti­fi­ca­tion can of­ten look clunky and coarse. Left-align­ing is more reliable.

But the choice is yours.