Mathematical Bold Small D 𝐝

Visual Description: The mathematical bold small d resembles a rounded lowercase d with a heavier stroke. It sits on the baseline and keeps a steady, compact form. In bold math fonts, the letter is slightly wider and more angular than ordinary text. It reads clearly next to other symbols.

Meaning & Usage: It marks a quantity in formulas or a special differential or placeholder. In equations, bold d helps separate a variable from ordinary letters. It signals emphasis or a distinct meaning, such as a dynamic quantity, a vector, or a parameter. In UI, it guides operators and comparisons.

Historical Background: Bold math letters emerged as printing and typesetting grew more precise. Designers created bold variants to reduce confusion when many symbols appear together. Over time, digital fonts adopted consistent bold styles for math, so a bold d behaves like other symbols in dense equations. The goal is clarity.

Practical Use: In formulas and calculators, the bold d can mark a differential or a special variable slot. Quick UI controls may snap to bold symbols to indicate an operation target or a comparison focus. Users glance at bold symbols to identify meaningful changes and keep workflows fast.

See our category page for related symbols.

Look‑alikes: d (U+64).

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