D, d
noun uk/diː/ us/diː/ Ds, D's or d's
(LETTER)
[ C or U ]（英语字母表的第四个字母）
the fourth letter of the English alphabet
(NUMBER)
[ C ] (also d)（罗马数字）500
the sign used in the Roman system for the number 500
(MUSIC)
[ C or U ]D 音;D 调
a note in Western music
in (the key of) D D 调
(FOOTBALL)
[ S ] UK（足球场上的）禁区弧
a D-shaped area on the edge of the penalty area of a football pitch
Players have to stand outside the D when a penalty is being taken. 罚点球时，其他球员必须站在禁区弧外。