- (mathematics) A mathematical function formally known as the Riemann zeta function.
- Lower-case zeta, the seventh letter of the ancient Greek alphabet. Its name was ζῆτα. The sound it represented is disputed, some claim it was /zd/, others claim it was /dz/. It is preceded by ϝ and followed by η.
- Lower-case zeta, the sixth letter of the modern Greek alphabet. Its name is ζήτα and it represents a voiced alveolar fricative: /z/. It is preceded by ε and followed by η.
- (Greek-script letters) Α α (A a), Β β (B b), Γ γ (G g), Δ δ (D d), Ε ε (E e), Ζ ζ (Z z), Η η (Ē ē), Θ θ (Th th), Ι ι ℩ (I i ℩), Κ κ (K k), Λ λ (L l), Μ μ (M m), Ν ν (N n), Ξ ξ (X x), Ο ο (O o), Π π (P p), Ρ ρ (R r), Σ σ ς (S s s), Τ τ (T t), Υ υ (U u), Φ φ (Ph ph), Χ χ (Kh kh), Ψ ψ (Ps ps), Ω ω (Ō ō)
- (punctuation) · ;
- (diacritics) ᾿ ῾ ´ ` ῀ ¨ ¯ ˘