Hy­phen­ation is the au­to­mated process of break­ing words be­tween lines to cre­ate more con­sis­tency across a text block.

In jus­ti­fied text, hy­phen­ation is mandatory.

In left-aligned text, hy­phen­ation evens the ir­reg­u­lar right edge of the text, called the rag. Hy­phen­ation is op­tional for left-aligned text be­cause the rag will still be some­what ir­reg­u­lar, even with hy­phen­ation. Hy­phen­ation doesn’t im­prove text leg­i­bil­ity. In this case, con­sider turn­ing it off.

As line length gets shorter, hy­phen­ation be­comes es­sen­tial. Why? With hy­phen­ation off, your word proces­sor can only break lines at word spaces. As the lines get shorter, there are fewer words and hence fewer pos­si­ble break points in each line, mak­ing awk­ward breaks more likely.

Some­times you may want to sup­press au­to­matic hy­phen­ation. For in­stance, head­ings are rel­a­tively short, so hy­phen­ation of­ten causes more prob­lems than it solves.

Hy­phen­ation can be sup­pressed in a sin­gle para­graph, or a set of para­graphs, if you sup­press hy­phen­ation within para­graph and char­ac­ter styles.