One suit plus winds or dragons, and nothing else.
Every tile is from one suit, plus honours. Winds and dragons are allowed in any number. A single tile from a second suit destroys it.
It is three faan. Removing the honours entirely turns it into Pure One Suit at seven, so the two are the same idea at different strictness.
This is the most practical big pattern in the game, because honours are allowed. Pick your suit by what you already hold and keep every honour you draw.
Discard the two dead suits in order, cheapest first. The hand telegraphs itself once you have discarded a whole suit, so expect defence.
Discarding honours to purify the hand. That is a move toward Pure One Suit, and it usually costs more than it gains. Honours are legal here and each dragon or seat wind pung adds a faan on top of the three.
It is the great combining pattern. With All Pungs it is three plus three for six. With a dragon pung it is four. Small Dragons plus Mixed One Suit is five plus three, eight faan. Most large hands in ordinary play pass through this row.
Can I use two suits if one is only a single tile?
No. One tile from a second suit ends the pattern. It is all of one suit or nothing.
Do I have to hold honours?
No. If you hold none you have Pure One Suit instead, which scores seven rather than three.
Is it worth breaking a good hand to reach it?
Usually not past the halfway point. Three faan is not worth a hand that never finishes.
Play Mahjong Winds
Every win shows its faan line by line, using the table on this page.