What are "full piece" and "half piece" in chess? I'm reading Kasparov's Deep Thinking and I came across this sentence:

In one computer championship, a machine blundered a full piece early
in the game but its opponent declined to capture it.

When I googled it I also saw the term &quot;half piece&quot; but couldn't find any definition on any of them.
I'm not a native speaker and I'm not familiar with chess terms in English. I'm guessing full piece is an important piece such as queen or rook and half piece is a minor piece like bishop or knight but I want to be sure. Can you explain what they mean?
blundering a full piece

or

being a full piece down

are typical expressions in English chess literature.
With the little word &quot;full&quot;, the author wants to make clear that the player has not only lost the piece, but that they also received no consolation material in return, i.e. one or two pawns. An alternative expression is &quot;blundering a clean piece&quot; / &quot;being a clean piece down&quot;.
The typical scale is:

The opponent blundered/sacrificed a piece for two pawns.
The opponent blundered/sacrificed a piece for a pawn.
The opponent blundered/sacrificed a full/clean piece.

(&quot;Sacrifice&quot; or &quot;blunder&quot; generally depend on the positional compensation for the loss of the piece.)
The &quot;piece&quot; in question may theoretically be a any of the &quot;pieces&quot; knight, bishop, rook or queen (pawns are not &quot;pieces&quot; and the king cannot be captured), but typically you would expect it to be either a knight or a bishop (in the other cases it would rather be e.g. &quot;being a full rook down&quot; or &quot;being a full queen down&quot;).
The term &quot;half piece&quot; does not exist, at least to my knowledge.