What Do X and C Mean on the NMJL Card?

On the NMJL card, X means a hand may be played exposed, while C means the hand must be played concealed. An X hand can include sets placed face-up after calling discards; a C hand cannot make those exposures, although it may claim a discard that completes Mah Jongg.

Where are X and C shown on the NMJL card?

Look at the end of each hand line on the current National Mah Jongg League card. Beside the printed point value, you will see either X or C.

That one letter controls how you may build the hand:

The X does not mean that you must expose tiles. You may keep an X hand hidden for as long as you want and reveal it only when you declare Mah Jongg.

What does X mean in American Mah Jongg?

An X hand is open to exposures. During play, you may call another player's most recent discard when that tile completes a legal group of three or more identical tiles required by your chosen card hand. You then place the completed group face-up on top of your rack.

For example, suppose your X hand needs a kong of 7 Dots and you hold three natural 7 Dots. When another player discards a 7 Dot, you may call it, expose all four 7 Dots, and then discard one tile to end your turn. That exposure commits those four tiles to exactly that group.

Before calling, check three things:

1. The hand's line ends in X.
2. The discarded tile completes a legal exposed group in that exact hand.
3. Every tile you place on top of the rack matches the number, suit, and group size shown on the card.

A discard cannot be called merely to make a pair or single. The exception is a discard that completes your entire winning hand, when you call Mah Jongg rather than exposing an incomplete hand.

What does C mean on the NMJL card?

A C hand must remain concealed. Draw tiles from the wall, keep the working hand on your rack, and discard normally, but do not call a discard to expose a pung, kong, or other group. Making even one ordinary exposure makes the concealed hand invalid.

There is one important winning-tile exception: if another player discards the exact tile that completes your C hand, you may call Mah Jongg and reveal the full hand for verification. You are not building an exposure at that point; you are completing the hand.

A concealed label also does not mean "no jokers." Jokers may fill eligible groups of three or more identical tiles in a C hand, but they still cannot represent a single or a pair. The tiles simply stay hidden on the rack until the win is declared.

A four-step check before you call a discard

When a useful tile lands in the discard area, pause for this quick check:

1. Find your exact line. Confirm the numbers, suits, spacing, and group sizes against the current NMJL card.
2. Read the final letter. X allows a normal exposure; C does not.
3. Identify the group. A normal call must complete a legal callable group, not merely improve your rack.
4. Test the remainder. After exposing, make sure the tiles left on your rack can still complete every other part of that same hand.

Imagine you are pursuing a C hand and hold two matching tiles needed for a pung. A third copy is discarded. Calling it would complete the pung, but it would also expose part of a hand the card requires you to conceal. The correct play is to let the tile go unless it completes Mah Jongg.

Now imagine the same group belongs to a hand marked X. You may call the third tile, place the pung above your rack, discard, and continue toward that X hand.

Common X and C mistakes

• Treating X as a requirement to expose. X gives permission; it does not force a call.
• Calling for part of a C hand. A concealed hand may claim a discard only when it completes Mah Jongg.
• Calling to complete a pair. Pairs and singles cannot be exposed through an ordinary discard call.
• Assuming concealed means jokerless. These are separate ideas. Eligible groups in a C hand may contain jokers.
• Switching to a C hand after exposing. Once tiles are exposed, they cannot fit a hand that must remain fully concealed.
• Reading only the tile pattern. The X or C label is part of the hand's instructions, just like its colors, parentheses, and point value.

Confirm your table's house rules before play.

How Bird Bam helps at the table

X-versus-C errors often surface only after several turns, when a group has already been exposed and the intended hand no longer works. Bird Bam helps groups keep hands, games, and scorekeeping organized, reducing the paper-tracking friction that can distract from checking the current NMJL card. Players still need the current card to select and verify a hand.

If your group wants a cleaner way to track play while everyone focuses on the card and the table, Bird Bam is a simple iOS companion for American Mah Jongg.

FAQ

Can I keep an X hand concealed?

Yes. X means exposures are allowed, not required. You can complete an X hand without exposing any groups.

Can I call the winning discard for a C hand?

Yes. You may claim a discard that completes the entire concealed hand and immediately declare Mah Jongg. You may not call earlier discards to build exposed groups.

Can a concealed hand use jokers?

Yes, when the jokers represent tiles in an eligible group of three or more identical tiles. Jokers cannot represent singles or pairs.

Does X stand for exposed and C stand for concealed?

Yes. Read the letter at the end of each NMJL card line before deciding whether to call a discard.