□

A square outline.

□

1. (geometry) A quadrilateral, usually referred to a square or rectangle.

   □ABCD

   A quadrilateral with vertices named A, B, C, and D in order.

2. A male family member in a family tree.

   Antonym: ○

3. (logic) logically necessary; provable

   Coordinate term: ◇

   • 2009, Logique et analyse, page 193:

     […] obtained by adding the standard modal operators □ (necessity) and ◇ (possibility) to paralogics.

4. (astrology) quadrature.
5. (alchemy) salt.

• ◻

• (logical necessity): ◊

□

1. Used as a placeholder for an illegible hanzi or lacuna.
2. Used as a placeholder for an unknown hanzi (as when discussing dialectal morphemes).
3. (Internet slang) Used in self-censorship of sensitive characters.

   alt. forms: 口 (kǒu)

• English: tofu
• Translingual: ⸢ ⸣, [ ]