This is a very interesting symbol in mathematics, which evolved from the English word Exist. Because the case of e is easy to be confused, so turning e upside down is the e in the mirror image. Existential quantifier means that some propositions A are B, which makes this proposition valid and is also used as a symbol in logic.

The outsole of mathematical symbols can be divided into the following categories:

Operation symbol: ×√.

Geometric symbols: ⊥∥∠⌒⊙≡≌△.

Algebraic symbols: ∧∧∨ ~ ∫≠≤≥≈∞.

Symbol set: ∩∩∈.

Special symbol: ∑ π (pi).

Inference symbol: | a|⊥∽△∠∩∪≠≡≥≤∈↓↓↖↗↘↙∥∥∥.； ① ② ③ ④ ⑤ ⑥ ⑦ ⑧ ⑨ ⑩……Γ Δ Θ Λ Ξ Ο Π Σ Φ Χ Ψ Ωα β γ δ ε ζ η θ ι κ λ μ νξ ο π ρ σ τ υ φ χ ψ ωⅠ Ⅱ Ⅲ Ⅳ Ⅴ Ⅵ Ⅶ Ⅷ Ⅸ Ⅹ Ⅺ Ⅻⅰ ⅱ ⅲ ⅳ ⅴ ⅵ ⅶ ⅷ ⅸ ⅹ∈ ∏ ∑ ∕ √ ∝ ∞ ∟ ∠ ∣ ∥ ∧ ∨ ∩ ∪ ∫ ∮∴ ∵ ∶ ∷ ∽ ≈ ≌ ≒ ≠ ≡ ≤ ≥ ≦ ≧ ≮ ≯ ⊕ ⊙ ⊥ ⊿ ⌒ ℃。