Answers.Body: <p>Adapted from <a href="https://en.wikipedia.org/wiki/Gambit#Soundness" rel="nofollow noreferrer">here</a>.</p>
  
  <p>A gambit is said to be '<strong>sound</strong>' if it is capable of resulting in an advantage against the opponent. <strong>There are three general criteria in which a gambit is often said to be sound:</strong></p>
  
  <ol>
  <li><strong>Time gain:</strong> the player accepting the gambit must take time to obtain the sacrificed material and possibly must use more time to reorganize his pieces after the material is taken.</li>
  <li><strong>Generation of differential activity:</strong> often a player accepting a gambit will decentralize his pieces or pawns and his poorly placed pieces will allow the gambiteer to place his own pieces and pawns on squares that might otherwise have been inaccessible. In addition, bishops and rooks can become more active simply because the loss of pawns often gives rise to open files and diagonals. </li>
  <li><strong>Generation of positional weaknesses:</strong> finally, accepting a gambit may lead to a compromised pawn structure, holes or other positional weaknesses.</li>
  </ol>
  
  <p>An example of a <strong>sound</strong> gambit is the Scotch Gambit: </p>
  
  <pre><code>[FEN ""]
  1.e4 e5 2.Nf3 Nc6 3.d4 exd4 4.Bc4. 
  </code></pre>
  
  <p>Here Black can force White to sacrifice a pawn speculatively with 4...Bb4+, but White gets very good compensation for one pawn after 5.c3 dxc3 6.bxc3, or for two pawns after 6.0-0 inviting 6...cxb2 7.Bxb2, due to the development advantage and attacking chances against the black king. As a result, Black is often advised not to try to hold on to the extra pawn.</p>
  
  <p>An example of an <strong>unsound</strong> gambit is the so-called Halloween Gambit: </p>
  
  <pre><code>[fen ""]
  1.e4 e5 2.Nf3 Nc6 3.Nc3 Nf6 4.Nxe5?! Nxe5 5.d4.
  </code></pre>
  
  <p>Here the investment (a knight for just one pawn) is too large for the moderate advantage of having a strong center. </p>
  
Answers.ContentLicense: CC BY-SA 4.0
Answers.CreationDate: 2019-07-30T04:57:55.410Z
Answers.Text: -1 This is copied almost verbatim from wikipedia.
Answers.UserDisplayName: Qudit
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Answers.Text: @Qudit to be fair this is a very reasonable explanation about the definition of soundness. What specifically is troubling you with this answer?
Answers.UserDisplayName: NoseKnowsAll
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Answers.CreationDate: 2019-07-30T08:16:48.280Z
Answers.Text: @NoseKnowsAll It's plagiarism which I find completely unacceptable.
Answers.UserDisplayName: Qudit
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Answers.CreationDate: 2019-07-30T08:25:27.783Z
Answers.Text: The fact that this answer is copied is not a problem by itself (this is not a school exam after all). The lack of proper citation is, however.
Answers.UserDisplayName: Annatar
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Answers.CreationDate: 2019-07-30T08:27:05.997Z
Answers.Text: I've added a link to the relevant article to the top of the answer.
Answers.UserDisplayName: vs97
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Answers.CreationDate: 2019-07-30T08:27:32.757Z
Answers.Text: @Annatar Agreed.
Answers.UserDisplayName: Qudit
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Answers.UserDisplayName: vs97
Answers.Body: <p>I would add to vs97's answer that not all sound openings lead to an advantage. Indeed, when playing Black, we are often happy with an equal game, thus defences that lead us there are "sound".</p>
  
  <p>Some openings that don't give anything special for White are still considered "sound" (I don't think anyone would say the London System is unsound). So I would say that for an opening to be unsound, it must have a clear refutation</p>
  
Answers.ContentLicense: CC BY-SA 4.0
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Answers.Text: Sure.  But that just raises the question of what constitutes a clear refutation.
Answers.UserDisplayName: Qudit
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Answers.Text: Well, pretty much nothing in chess, apart from the pieces, is either Black or White. An opening may be "refuted" and still be played by some people becuase they like the resulting position for some reason
Answers.UserDisplayName: David
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Answers.Text: That is true.  But this question is about a precise definition of soundness and I still am not sure what exactly is meant by the term.
Answers.UserDisplayName: Qudit
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Answers.Text: What makes you think there is a precise definition? If there were, who would have the authority to determine what that definition is? An "unsound" opening is just an opening that is not advisable to play because it will create no trouble to a prepared opponent. That's what most people would understand, but there may be subtle differences for each player. This is chess, not logic nor math. It's like asking for a definition of the difference between an imprecision, a bad move and a blunder There is just no "border"
Answers.UserDisplayName: David
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Answers.CreationDate: 2019-07-30T08:30:37.217Z
Answers.Text: I would hope that it could at least be defined qualitatively in terms of chess terms. I put some example questions in the original post.
Answers.UserDisplayName: Qudit
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Answers.CreationDate: 2019-07-30T08:32:45.097Z
Answers.Text: "Some openings that don't give anything special for White are still considered sound". From this you get that White losing the starting advantage is not always enough for an opening to be regarder as "unsound". Black staying better probably is, though
Answers.UserDisplayName: David
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Answers.UserDisplayName: David
Body: <p>What exactly does it mean for a gambit to be unsound?  I see this term being used a lot but I have yet to come across a precise definition.  </p>
  
  <p>Is it enough for white to lose the  advantage that comes with being the first player?  What if black is better with best play but not winning?</p>
  
  <p>How is soundness defined if black is the one playing the gambit?</p>
  
Tags: <opening><gambits><terminology>
Title: Definition of Soundness
ThreadText: # Definition of Soundness
  
  (Asked by: username_0 on 2019-07-29)
  
  What exactly does it mean for a gambit to be unsound? I see this term being used a lot but I have yet to come across a precise definition.
  
  Is it enough for white to lose the advantage that comes with being the first player? What if black is better with best play but not winning?
  
  How is soundness defined if black is the one playing the gambit?
  
  **Tags:** opening, gambits, terminology
  
  
  ---
  
  ## 2 answers
  
  ### Answer by username_1 on 2019-07-29. Score: 6
  
  Adapted from here.
  A gambit is said to be 'sound' if it is capable of resulting in an advantage against the opponent. There are three general criteria in which a gambit is often said to be sound:
  
  Time gain: the player accepting the gambit must take time to obtain the sacrificed material and possibly must use more time to reorganize his pieces after the material is taken.
  Generation of differential activity: often a player accepting a gambit will decentralize his pieces or pawns and his poorly placed pieces will allow the gambiteer to place his own pieces and pawns on squares that might otherwise have been inaccessible. In addition, bishops and rooks can become more active simply because the loss of pawns often gives rise to open files and diagonals. 
  Generation of positional weaknesses: finally, accepting a gambit may lead to a compromised pawn structure, holes or other positional weaknesses.
  
  An example of a sound gambit is the Scotch Gambit: 
  [FEN ""]
  1.e4 e5 2.Nf3 Nc6 3.d4 exd4 4.Bc4. 
  
  Here Black can force White to sacrifice a pawn speculatively with 4...Bb4+, but White gets very good compensation for one pawn after 5.c3 dxc3 6.bxc3, or for two pawns after 6.0-0 inviting 6...cxb2 7.Bxb2, due to the development advantage and attacking chances against the black king. As a result, Black is often advised not to try to hold on to the extra pawn.
  An example of an unsound gambit is the so-called Halloween Gambit: 
  [fen ""]
  1.e4 e5 2.Nf3 Nc6 3.Nc3 Nf6 4.Nxe5?! Nxe5 5.d4.
  
  Here the investment (a knight for just one pawn) is too large for the moderate advantage of having a strong center.
  
  > **Comments:**
  > **username_0**: -1 This is copied almost verbatim from wikipedia.  
  > **username_2**: @username_0 to be fair this is a very reasonable explanation about the definition of soundness. What specifically is troubling you with this answer?  
  > **username_0**: @username_2 It's plagiarism which I find completely unacceptable.  
  > **username_3**: The fact that this answer is copied is not a problem by itself (this is not a school exam after all). The lack of proper citation is, however.  
  > **username_1**: I've added a link to the relevant article to the top of the answer.  
  > **username_0**: @username_3 Agreed.  
  
  ---
  
  ### Answer by username_4 on 2019-07-30. Score: 1
  
  I would add to username_1's answer that not all sound openings lead to an advantage. Indeed, when playing Black, we are often happy with an equal game, thus defences that lead us there are "sound".
  
  Some openings that don't give anything special for White are still considered "sound" (I don't think anyone would say the London System is unsound). So I would say that for an opening to be unsound, it must have a clear refutation
  
  > **Comments:**
  > **username_0**: Sure.  But that just raises the question of what constitutes a clear refutation.  
  > **username_4**: Well, pretty much nothing in chess, apart from the pieces, is either Black or White. An opening may be "refuted" and still be played by some people becuase they like the resulting position for some reason  
  > **username_0**: That is true.  But this question is about a precise definition of soundness and I still am not sure what exactly is meant by the term.  
  > **username_4**: What makes you think there is a precise definition? If there were, who would have the authority to determine what that definition is? An "unsound" opening is just an opening that is not advisable to play because it will create no trouble to a prepared opponent. That's what most people would understand, but there may be subtle differences for each player. This is chess, not logic nor math. It's like asking for a definition of the difference between an imprecision, a bad move and a blunder There is just no "border"  
  > **username_0**: I would hope that it could at least be defined qualitatively in terms of chess terms. I put some example questions in the original post.  
  > **username_4**: "Some openings that don't give anything special for White are still considered sound". From this you get that White losing the starting advantage is not always enough for an opening to be regarder as "unsound". Black staying better probably is, though  
  
  ---
  
  