is 1 . Every tile is 2 through 8. A 1, a 9, or any honor removes it.
The name players use is tanyao (断么九). This site's glossary also lists it as All Simples.
Open or closed
The han stays when you call. , , and an are allowed, and the yaku is still 1 han. The EMA 2016 rules put that on the list. The edition before them scored tanyao only on a . and Mahjong Soul allow the open hand too. The yaku list states the same rule.
This waits on . The pair is not finished yet. Every tile is 2 through 8, so the hand is tanyao. The wait is a single tile, so the hand is not pinfu.
The glossary entry is the short form: no terminals and no honors.
What a simple open hand pays
An open hand with no extra fu is 20 fu, and that rounds up to 30. At 1 han 30 fu, a collects 1,000. The dealer collects 1,500. Those payments have no and no sticks.
A closed tanyao won by tsumo also has menzen tsumo, so count that han too.
What sits with it
can sit in the same closed hand when the pair is not and the wait is two-sided. An honor removes tanyao, and honitsu requires one, so a hand is never tanyao. A one-suit hand with no honors is chinitsu. Tanyao can sit in that hand when every tile is still 2 through 8.
Price a tanyao hand
The score calculator turns 1 han 30 fu, the open hand with no extra fu, into 1,000 or 1,500. Add honba when the table has them.
Open the score calculator