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* [[Iipeiko]]
* [[Iipeiko]]
* [[Chinitsu]]
* [[Chinitsu]]
|gameExample = * [http://tenhou.net/0/?log=2013010402gm-0009-7447-x1ba0b4910bee&tw=3&ts=7 Closed ittsu]
|gameExample = * [http://tenhou.net/0/?log=2013010402gm-0009-7447-x1ba0b4910bee&tw=3&ts=7 Closed ittsuu]
* [http://tenhou.net/0/?log=2014030918gm-0089-0000-22ae5fde&tw=2&ts=6 Ittsu] as [[kazoe]]
* [http://tenhou.net/0/?log=2014030918gm-0089-0000-22ae5fde&tw=2&ts=6 Ittsuu] as [[kazoe]]
}}
}}
'''Ikkitsuukan''' {{kana|一気通貫}}, or '''ittsu''' {{kana|一通}} for short, is one of the standard [[List of yaku|yaku]]. This hand contains three [[mentsu|tile groups]] in one suit of 1 through 9. By English terms, this hand can also be noted as a "straight", similar to the poker hand of the same name. This hand may be open or closed.
'''Ikkitsuukan''' {{kana|一気通貫}}, or '''ittsuu''' {{kana|一通}} for short, is a standard [[List of yaku|yaku]], defined as three distinct [[mentsu|tile groups]] containing 123, 456, 789 of one suit. This forms a single suit "straight" of 123456789, similar to the poker hand. This yaku can be scored open or closed, but if in an open hand, it [[kuisagari|loses 1 han]] of value.


==Tile diagram==
==Tile diagram==
Line 22: Line 22:


==Formation==
==Formation==
While the hand shows a complete 1-9 grouping from a particular suit, it is best to view the long cluster as three separate groups of: 123, 456, and 789. This is particularly useful to note when needing to open the hand with such a combination.  For example, having tile groups of 123, 345, 678, and 789 does not compose this yaku, despite possessing all 1-9 in the hand.
While ittsu appears as a complete 1-9 string, it is only scored if you have the sequences of 123, 456, 789. The following hand, while it contains every tile from 1-9, does not qualify for this yaku:


===Counter example===
{{#mjt:12344m56p}} {{#mjt:5'677'89m}} Waiting for: {{#mjt:4p}} or {{#mjt:7p}}
{{#mjt:12344m56p}} {{#mjt:5'677'89m}} Waiting for: {{#mjt:4p}} or {{#mjt:7p}}


In this counter example, the tiles 1-9 for one suit are in the hand.  However, ittsu would not be counted.  In fact, this hand is lacks any yaku.  The manzu are not grouped as 123, 456, and 789.  Instead, they are grouped as 123, 567, and 789.  The 4-man function as the [[Jantou|pair]] rather than belong to any of the [[shuntsu|sequences]].
This hand cannot score ittsu because the tiles are grouped as 123, 567, and 789, with 4-man functioning as the [[Jantou|pair]].


== Compatability ==
===Discard characteristics===
{{main|Yaku compatability}}
Hands aiming for ittsu often lack a particular suit, as a good number of one suit is collected in the hand.


{{yakuheader}}
== Compatibility ==
| ITT || {{yes}} || {{yes}} || {{yes}} || {{yes}} || {{no}} || {{yes}} || {{yes}} ||bgcolor="000000"|  || {{yes}} || {{no}} || {{no}} || {{no}} || {{no}} || {{no}} || {{no}} || {{no}} || {{no}} || {{no}} || {{no}} || {{yes}} || {{yes}} || {{no}} || {{yes}} || {{yes}} || {{yes}} || {{yes}}
{{main|Yaku compatibility}}
|}


Ittsu requires three out of the four tile groups to be composed of sequences: 123, 456, and 789.  That may only leave room for one tile group of any type, such as a triplet; and so, any yaku that requires more than one triplet is deemed incompatible.
{{Yaku compatibility table|ITT}}


=== With pinfu ===
Ittsu requires three groups to be sequences, leaving room for only one other tile group. Yaku that require more than one triplet - [[sanshoku doukou]], [[sanankou]], [[sankantsu]], [[shousangen]], [[toitoi]] - are thus incompatible. Similarly, [[sanshoku]] and [[ryanpeikou]] are incompatible because there is no room for their patterns. [[Chiitoitsu]], which does not use [[mentsu]], is likewise incompatible. The 456 sequence invalidates [[chanta]], [[junchan]], and [[honroutou]], while the 123 and 789 sequences invalidate [[tanyao]].  
[[Pinfu]] requires a [[machi|wait pattern]] of either [[ryanmen]] (open wait) or [[ryanmenten]] (three sided open).  Any other wait pattern disqualifies pinfu. Ryanmen waits on two tile types, while ryanmenten waits on three tile types. Both of these wait patterns regarding ittsu are subject to [[takame and yasume]], where only one tile type produces a winning hand of higher value.  Winning on that one tile would produce ittsu; while the others do not.  However, this problem is completely averted if the hand contains the full 1-9 pattern. Thus, the waiting tiles depend on the extra tile group, which renders the problem moot.


=== With honitsu and chinitsu ===
Ittsu can often be combined with [[honitsu]]/[[chinitsu]], as the ittsu is already composed of 9 tiles of the same suit. [[Pinfu]] also combines well; however, if the ittsu section is not complete, the hand would be subject to to [[takame and yasume]] (only one of two waiting tiles would score this yaku).
The development of [[honitsu]] and [[chinitsu]] with ittsu is made easier, when nine tiles (1-9) out of the thirteen of the hand is already single suited.  That leaves the remaining four (plus one winning tile) to be composed of the same suit or an honor tile. But once again, in the case of pinfu, takame and yakume may apply here, if applicable.


With closed hands, this combination produces some very powerful hands.  With honitsu, the hand produces [[mangan]]; while it is [[haneman]] with chinitsu.
===Vs sanshoku===
{{main|Ittsu vs sanshoku}}
Ittsuu requires three out of the four tile groups to be composed of sequences: 123, 456, and 789.  Sanshoku also requires at least three groups of sequences.  Sometimes, a hand may be 1-shanten for both yaku because of composition, forcing players to decide one or the other.
 
==Usage==
Despite being easy to memorize, ittsu is one of the more difficult yaku to obtain.
 
[[Sanshoku]] is worth the same (2 han) and has a similar requirement (3 specific sequences). However, sanshoku occurs in winning hands more than twice as often as ittsu. This is likely because ittsu's 123 and 789 sequences are harder to form than other sequences.


==External links==
==External links==

Latest revision as of 00:24, 11 August 2024

Ikkitsuukan 「一気通貫」, or ittsuu 「一通」 for short, is a standard yaku, defined as three distinct tile groups containing 123, 456, 789 of one suit. This forms a single suit "straight" of 123456789, similar to the poker hand. This yaku can be scored open or closed, but if in an open hand, it loses 1 han of value.

Ikkitsuukan
Type Yaku
Kanji 一通 or 一気通貫
English Straight
Value 2 han
1 han (open)
Speed Fast
Difficulty Easy

Tile diagram

              Winning tile:   or  

Open

                Winning tile:  

Formation

While ittsu appears as a complete 1-9 string, it is only scored if you have the sequences of 123, 456, 789. The following hand, while it contains every tile from 1-9, does not qualify for this yaku:

               Waiting for:   or  

This hand cannot score ittsu because the tiles are grouped as 123, 567, and 789, with 4-man functioning as the pair.

Discard characteristics

Hands aiming for ittsu often lack a particular suit, as a good number of one suit is collected in the hand.

Compatibility

Main article: Yaku compatibility

^ Ippatsu requires riichi to be of any use.

RCH DRI IPP SMO TAN PFU IPK ITT YAK SDJ SDO TOI SNA SNK CHA JUN RPK SSG HRO HON CHN CHI RIN HAI HOU CHK
ITT                                                  

Ittsu requires three groups to be sequences, leaving room for only one other tile group. Yaku that require more than one triplet - sanshoku doukou, sanankou, sankantsu, shousangen, toitoi - are thus incompatible. Similarly, sanshoku and ryanpeikou are incompatible because there is no room for their patterns. Chiitoitsu, which does not use mentsu, is likewise incompatible. The 456 sequence invalidates chanta, junchan, and honroutou, while the 123 and 789 sequences invalidate tanyao.

Ittsu can often be combined with honitsu/chinitsu, as the ittsu is already composed of 9 tiles of the same suit. Pinfu also combines well; however, if the ittsu section is not complete, the hand would be subject to to takame and yasume (only one of two waiting tiles would score this yaku).

Vs sanshoku

Main article: Ittsu vs sanshoku

Ittsuu requires three out of the four tile groups to be composed of sequences: 123, 456, and 789. Sanshoku also requires at least three groups of sequences. Sometimes, a hand may be 1-shanten for both yaku because of composition, forcing players to decide one or the other.

Usage

Despite being easy to memorize, ittsu is one of the more difficult yaku to obtain.

Sanshoku is worth the same (2 han) and has a similar requirement (3 specific sequences). However, sanshoku occurs in winning hands more than twice as often as ittsu. This is likely because ittsu's 123 and 789 sequences are harder to form than other sequences.

External links

Ikkitsuukan in Japanese Wikipedia
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