Iota
| Greek letters | |
| Α α Alpha | Β β Beta |
| Γ γ Gamma | Δ δ Delta |
| Ε ε Epsilon | Ϝ ϝ Digamma |
| Ζ ζ Zeta | Η η Eta |
| Θ θ Theta | Ι ι Iota |
| Κ κ Kappa | Λ λ Lambda |
| Μ μ Mu | Ν ν Nu |
| Ξ ξ Xi | Ο ο Omicron |
| Π π Pi | Ϻ ϻ San |
| Ϙ ϙ Qoppa | Ρ ρ Rho |
| Σ σ Sigma | Τ τ Tau |
| Υ υ Upsilon | Φ φ Phi |
| Χ χ Chi | Ψ ψ Psi |
| Ω ω Omega | Ϡ ϡ Sampi |
| Greek alphabet | |
Iota (upper case Ι, lower case ι) is the 9th letter of the Greek alphabet. In the system of Greek numerals it has a value of 10.
The word iota is also used in English to express a very small amount. By some accounts this usage stems from the third- and fourth-century theological dispute over the Arian doctrine that Jesus and God the Father were of distinct but similar substances—Greek homoi-ousios—against the orthodox doctrine that they are one substance—Greek homo-ousios. The two words differ by one iota.
Letters that arose from Iota include the Roman I.