I guess the complete page of terms is in the glossary?
Verification and certification:
Best defence - The strongest opposing reply within the scope declared by the verification.
This is basically "best move". (It's actually quite hard to define defense since offense can be defense, but in general the goal of a defensive move is prophylaxis / preventing your opponent from doing something. Since "best move" doesn't exist in verification and certification I assume this is supposed to be best move/best response instead of best defense)
Oh wait, in the context of "goal" the term "best defence" makes sense.
Verification - Control of the claim through a procedure capable of contradicting the detection.
Unclear so: "To perform a procedure capable of showing that a claim is either contradicted or certified."
Chess:
Capture - A move that removes an opponent’s piece from the board by landing on its square.
En passant is a capture
Check - A position in which the side to move’s king is attacked.
A move is called a "check" if it attacks the opponent's king.
A king is "in check" when it is attacked.
Diagonal - A line of squares of one colour running at an angle across the board.
FIDE laws of chess is more precise:

Draw - A game that ends without a winner.
Technically there are some over-the-board games (and even online daily chess games) which were ruled as 0-0 i.e. both players lost. Which is not really a draw. This definition is perfectly fine imo, but technically the true definition is: "stalemate, insufficient material or dead position, agreement, timeout vs insufficient material or dead position, repetition, fifty or seventy-five move rule"
Gain - The material a side ends up ahead after the sequence under study, against the opponent’s best defence.
Looks like best defence is in two categories.
Screen - A piece standing on a line between a long-range attacker and another piece further along that line.
I haven't heard of that personally. Relevant but different concepts are x-ray and interference.
Sequence - The moves played from the position shown, by both sides in turn, that a claim is read over.
(Also see combination) Note that a puzzle often involves more than one line, so this seems to not work
Tactic - A short forcing operation that gains material or mates, resolved within a few moves against best defence.
Especially with pawn endgames, a tactic just has to end up in a winning position. So actually gaining material or checkmate make take ages under best defense even though it's clearly just winning.
I guess the complete page of terms is in the glossary?
Verification and certification:
> Best defence - The strongest opposing reply within the scope declared by the verification.
This is basically "best move". (It's actually quite hard to define defense since offense can be defense, but in general the goal of a defensive move is prophylaxis / preventing your opponent from doing something. Since "best move" doesn't exist in verification and certification I assume this is supposed to be best move/best response instead of best defense)
Oh wait, in the context of "goal" the term "best defence" makes sense.
> Verification - Control of the claim through a procedure capable of contradicting the detection.
Unclear so: "To perform a procedure capable of showing that a claim is either contradicted or certified."
---
Chess:
> Capture - A move that removes an opponent’s piece from the board by landing on its square.
En passant is a capture
> Check - A position in which the side to move’s king is attacked.
A move is called a "check" if it attacks the opponent's king.
A king is "in check" when it is attacked.
> Diagonal - A line of squares of one colour running at an angle across the board.
FIDE laws of chess is more precise:

> Draw - A game that ends without a winner.
Technically there are some over-the-board games (and even online daily chess games) which were ruled as 0-0 i.e. both players lost. Which is not really a draw. This definition is perfectly fine imo, but technically the true definition is: "stalemate, insufficient material or dead position, agreement, timeout vs insufficient material or dead position, repetition, fifty or seventy-five move rule"
> Gain - The material a side ends up ahead after the sequence under study, against the opponent’s best defence.
Looks like best defence is in two categories.
> Screen - A piece standing on a line between a long-range attacker and another piece further along that line.
I haven't heard of that personally. Relevant but different concepts are x-ray and interference.
> Sequence - The moves played from the position shown, by both sides in turn, that a claim is read over.
(Also see combination) Note that a puzzle often involves more than one line, so this seems to not work
> Tactic - A short forcing operation that gains material or mates, resolved within a few moves against best defence.
Especially with pawn endgames, a tactic just has to end up in a winning position. So actually gaining material or checkmate make take ages under best defense even though it's clearly just winning.