But there is more to it than that. In fact, doing good haiku is hard. That's why I keep doing it. I haven't done a good one yet.
The precursor to the garden-variety 5-7-5 pattern was called thanka (or waka) and it has a 5-7-5-7-7 pattern. In a variation of that, one writer can write the 5-7-5 thanka opening, and someone else can write the last two lines. It's a poetic word game for two.
It reminds me of what Jane Hirshfield said in her Kindle Single, The Heart of Haiku:
To read a haiku is to become its co-author, to place yourself inside its words until they reveal one of the proteus-shapes of your own life.Of course, such an exercise is different for everyone.
See if you can add anything to this haiku:
in mad defiance
i will light the light again