TeXipedia

blacksquare

Represents a solid black square symbol commonly used to mark the end of proofs or as a visual marker in mathematical writing.

Overview

Serves as a formal notation in mathematical documents, particularly in academic and professional contexts.

  • Traditionally used as a "QED" symbol to denote the completion of mathematical proofs
  • Functions as a visual separator or marker in mathematical texts and textbooks
  • Often preferred over the hollow square (\square) when stronger visual emphasis is needed
  • Commonly appears in theoretical mathematics, computer science proofs, and formal logic documents
  • Can also serve as a bullet point or visual element in specialized mathematical lists or enumerations

Examples

End of proof marker (QED symbol) in a mathematical proof.

x2+2x+1=(x+1)2■x^2 + 2x + 1 = (x + 1)^2 \blacksquare 
x^2 + 2x + 1 = (x + 1)^2 \blacksquare

Binary state indicator in a truth table.

P∧Q  ⟹  R■P \land Q \implies R \quad \blacksquare 
P \land Q \implies R \quad \blacksquare

Filled square bullet point in an important mathematical statement.

f(x) is continuous on [a,b]■f(x) \text{ is continuous on } [a,b] \blacksquare 
f(x) \text{ is continuous on } [a,b] \blacksquare