Calling for a pair, a single, or a concealed hand

Can I call a discard for a pair, a single, or a concealed hand?

Question 1 of up to 2

Would this discard be your 14th tile and complete the whole hand, so that you can declare Mah Jongg right now?

Read every possible ruling for this situation

Mahjongg any tile

Yes — any tile but a Joker can be called for Mah Jongg

Standard rule
Yes. Any discarded tile except a Joker can be called for Mah Jongg, no matter where it fits in the hand — a single, one of a pair, part of NEWS or a year, or the last tile of a pung or kong. This is true for a concealed hand too; calling the winning tile is the one time a concealed hand may take a discard.
Why
The winning tile completes the hand outright, so there is no partial exposure to make and nothing left to build.
Common house rules
None that we know of. This one is played the same way at nearly every table.

If your table agreed on a house rule before the game, that rule wins.

Under review by instructors

Sources consulted: Mahj Life Rules Wiki, Article 178 (Any Tile Can Be Called for Mah Jongg); Mahj Life Rules Wiki, Article 22 (Claiming a Discard When Playing a Concealed Hand); Tom Sloper, Mah-Jongg FAQ 19 (American rules): “Can I say mah-jongg on a discard if I'm waiting for a single or to complete a pair?”; AMJA, The Complete American Mah Jongg Rulebook, FAQ: claiming a discarded tile for Mah Jongg to complete a Single or Pair

Ok to expose

Yes — call it and expose the group

Standard rule
You may call it. During play a discard can be claimed to expose a pung, kong, quint, or sextet — three or more identical tiles — as long as your hand is not marked concealed. Say your call out loud, place the discard on top of your rack, and put up the rest of the group, Jokers included if you are using any. The whole group goes up now; a Joker picked up later in the turn cannot be added to it.
Why
Exposures are limited to groups of identical tiles so that every exposure gives the table real, checkable information about the hand.
Common house rules
None that we know of. This one is played the same way at nearly every table.

If your table agreed on a house rule before the game, that rule wins.

Under review by instructors

Sources consulted: Mahj Life Rules Wiki, Article 146 (Calling a Discard to Expose a Block with Singles); Mahj Life Rules Wiki, Article 125 (Discards Cannot Be Called to Complete a Pair); Tom Sloper, Mah-Jongg FAQ 19 (American rules): “A discard may only be taken to make a PUNG, KONG, QUINT, or SEXTET” and “Is there a limit to how many jokers I can use in a set?”; AMJA, The Complete American Mah Jongg Rulebook, FAQ: can a player claim a discarded tile and expose a Pair

Not callable

Not callable — leave it on the table

Standard rule
This discard cannot be called. During play a discard may only be taken to expose a pung, kong, quint, or sextet. It cannot be taken to make a pair, to fill a single, or to put up a group of different tiles such as NEWS or a year, and a hand marked concealed cannot take any discard except its winning tile. Taking it anyway creates an incorrect exposure, and another player may call the hand dead. The tile stays on the table for anyone who can use it properly.
Why
Pairs and singles are the parts of a hand you are meant to draw yourself; that difficulty is built into the game.
Common house rules
Some beginner tables relax this while learning. It changes the balance of the game, so if your group does it, make sure everyone knows before the first deal.

If your table agreed on a house rule before the game, that rule wins.

Under review by instructors

Sources consulted: Mahj Life Rules Wiki, Article 125 (Discards Cannot Be Called to Complete a Pair); Mahj Life Rules Wiki, Article 146 (Calling a Discard to Expose a Block with Singles); Mahj Life Rules Wiki, Article 22 (Claiming a Discard When Playing a Concealed Hand); Tom Sloper, Mah-Jongg FAQ 19 (American rules): “Can I kong a 202x or a NEWS?” and “What do the terms exposed and concealed mean?”; AMJA, The Complete American Mah Jongg Rulebook, FAQ: can a player claim a discarded tile and expose a Pair

All rules