also: ディ
The letter D/d itself, used as a symbol, grade, musical note, or in abbreviations.
Grades are on a four-level scale: A, B, C, D.
This piece starts in D major.
Colloquial abbreviation for ディレクター (director), used in film, TV, or project contexts.
I heard that famous director worked on this commercial.
Katakana spelling, often used in explanations or when the letter shape is not needed.
Full-width lowercase d; less common than uppercase.
From English letter name 'dee' and abbreviation of 'director'.