<P> In its classical and modern forms, the alphabet has 24 letters, ordered from alpha to omega . Like Latin and Cyrillic, Greek originally had only a single form of each letter; it developed the letter case distinction between upper - case and lower - case forms in parallel with Latin during the modern era . </P> <P> Sound values and conventional transcriptions for some of the letters differ between Ancient Greek and Modern Greek usage, because the pronunciation of Greek has changed significantly between the 5th century BC and today . Modern and Ancient Greek use different diacritics . The traditional orthography, which is used for Ancient Greek and sometimes for Modern Greek, has many diacritics, such as accent marks for pitch accent ("polytonic"), the breathing marks for the presence and absence of the initial / h / sound, and the iota subscript for the final historical / i / sound . In standard Modern Greek spelling, orthography has been simplified to a monotonic system, which uses only two diacritics: the acute accent and diaeresis . </P> <Table> <Tr> <Td> <Table> <Tr> <Th> Letter </Th> <Th> Name </Th> <Th_colspan="2"> Sound </Th> </Tr> <Tr> <Th> Ancient </Th> <Th> Modern </Th> </Tr> <Tr> <Td> Α α </Td> <Td> alpha, άλφα </Td> <Td> (a) (aː) </Td> <Td> </Td> </Tr> <Tr> <Td> Β β </Td> <Td> beta, βήτα </Td> <Td> </Td> <Td> </Td> </Tr> <Tr> <Td> Γ γ </Td> <Td> gamma, γάμμα </Td> <Td> (ɡ), (ŋ) </Td> <Td> (ɣ) ~ (ʝ), (ŋ) ~ (ɲ) </Td> </Tr> <Tr> <Td> Δ δ </Td> <Td> delta, δέλτα </Td> <Td> (d) </Td> <Td> (ð) </Td> </Tr> <Tr> <Td> Ε ε </Td> <Td> epsilon, έψιλον </Td> <Td_colspan="2"> </Td> </Tr> <Tr> <Td> Ζ ζ </Td> <Td> zeta, ζήτα </Td> <Td> (zd) </Td> <Td> (z) </Td> </Tr> <Tr> <Td> Η η </Td> <Td> eta, ήτα </Td> <Td> (ɛː) </Td> <Td> (i) </Td> </Tr> <Tr> <Td> Θ θ </Td> <Td> theta, θήτα </Td> <Td> (th) </Td> <Td> (θ) </Td> </Tr> <Tr> <Td> Ι ι </Td> <Td> iota, ιώτα </Td> <Td> (i) (iː) </Td> <Td> (i), (ʝ), (ɲ) </Td> </Tr> <Tr> <Td> Κ κ </Td> <Td> kappa, κάππα </Td> <Td> (k) </Td> <Td> (k) ~ (c) </Td> </Tr> <Tr> <Td> Λ λ </Td> <Td> lambda, λάμδα </Td> <Td_colspan="2"> (l) </Td> </Tr> <Tr> <Td> Μ μ </Td> <Td> mu, μυ </Td> <Td_colspan="2"> (m) </Td> </Tr> </Table> Or (dz). </Td> <Td> <Table> <Tr> <Th> Letter </Th> <Th> Name </Th> <Th_colspan="2"> Sound </Th> </Tr> <Tr> <Th> Ancient </Th> <Th> Modern </Th> </Tr> <Tr> <Td> Ν ν </Td> <Td> nu, νυ </Td> <Td_colspan="2"> (n) </Td> </Tr> <Tr> <Td> Ξ ξ </Td> <Td> xi, ξι </Td> <Td_colspan="2"> (ks) </Td> </Tr> <Tr> <Td> Ο ο </Td> <Td> omicron, όμικρον </Td> <Td_colspan="2"> (o) </Td> </Tr> <Tr> <Td> Π π </Td> <Td> pi, πι </Td> <Td_colspan="2"> (p) </Td> </Tr> <Tr> <Td> Ρ ρ </Td> <Td> rho, ρώ </Td> <Td_colspan="2"> (r) </Td> </Tr> <Tr> <Td> Σ σ / ς </Td> <Td> sigma, σίγμα </Td> <Td> (s) </Td> <Td> (s) ~ (z) </Td> </Tr> <Tr> <Td> Τ τ </Td> <Td> tau, ταυ </Td> <Td_colspan="2"> </Td> </Tr> <Tr> <Td> Υ υ </Td> <Td> upsilon, ύψιλον </Td> <Td> (y) (yː) </Td> <Td> (i) </Td> </Tr> <Tr> <Td> Φ φ </Td> <Td> phi, φι </Td> <Td> (ph) </Td> <Td> (f) </Td> </Tr> <Tr> <Td> Χ χ </Td> <Td> chi, χι </Td> <Td> (kh) </Td> <Td> (x) ~ (ç) </Td> </Tr> <Tr> <Td> Ψ ψ </Td> <Td> psi, ψι </Td> <Td_colspan="2"> (ps) </Td> </Tr> <Tr> <Td> Ω ω </Td> <Td> omega, ωμέγα </Td> <Td> (ɔː) </Td> <Td> (o) </Td> </Tr> </Table> </Td> </Tr> </Table> <Tr> <Td> <Table> <Tr> <Th> Letter </Th> <Th> Name </Th> <Th_colspan="2"> Sound </Th> </Tr> <Tr> <Th> Ancient </Th> <Th> Modern </Th> </Tr> <Tr> <Td> Α α </Td> <Td> alpha, άλφα </Td> <Td> (a) (aː) </Td> <Td> </Td> </Tr> <Tr> <Td> Β β </Td> <Td> beta, βήτα </Td> <Td> </Td> <Td> </Td> </Tr> <Tr> <Td> Γ γ </Td> <Td> gamma, γάμμα </Td> <Td> (ɡ), (ŋ) </Td> <Td> (ɣ) ~ (ʝ), (ŋ) ~ (ɲ) </Td> </Tr> <Tr> <Td> Δ δ </Td> <Td> delta, δέλτα </Td> <Td> (d) </Td> <Td> (ð) </Td> </Tr> <Tr> <Td> Ε ε </Td> <Td> epsilon, έψιλον </Td> <Td_colspan="2"> </Td> </Tr> <Tr> <Td> Ζ ζ </Td> <Td> zeta, ζήτα </Td> <Td> (zd) </Td> <Td> (z) </Td> </Tr> <Tr> <Td> Η η </Td> <Td> eta, ήτα </Td> <Td> (ɛː) </Td> <Td> (i) </Td> </Tr> <Tr> <Td> Θ θ </Td> <Td> theta, θήτα </Td> <Td> (th) </Td> <Td> (θ) </Td> </Tr> <Tr> <Td> Ι ι </Td> <Td> iota, ιώτα </Td> <Td> (i) (iː) </Td> <Td> (i), (ʝ), (ɲ) </Td> </Tr> <Tr> <Td> Κ κ </Td> <Td> kappa, κάππα </Td> <Td> (k) </Td> <Td> (k) ~ (c) </Td> </Tr> <Tr> <Td> Λ λ </Td> <Td> lambda, λάμδα </Td> <Td_colspan="2"> (l) </Td> </Tr> <Tr> <Td> Μ μ </Td> <Td> mu, μυ </Td> <Td_colspan="2"> (m) </Td> </Tr> </Table> Or (dz). </Td> <Td> <Table> <Tr> <Th> Letter </Th> <Th> Name </Th> <Th_colspan="2"> Sound </Th> </Tr> <Tr> <Th> Ancient </Th> <Th> Modern </Th> </Tr> <Tr> <Td> Ν ν </Td> <Td> nu, νυ </Td> <Td_colspan="2"> (n) </Td> </Tr> <Tr> <Td> Ξ ξ </Td> <Td> xi, ξι </Td> <Td_colspan="2"> (ks) </Td> </Tr> <Tr> <Td> Ο ο </Td> <Td> omicron, όμικρον </Td> <Td_colspan="2"> (o) </Td> </Tr> <Tr> <Td> Π π </Td> <Td> pi, πι </Td> <Td_colspan="2"> (p) </Td> </Tr> <Tr> <Td> Ρ ρ </Td> <Td> rho, ρώ </Td> <Td_colspan="2"> (r) </Td> </Tr> <Tr> <Td> Σ σ / ς </Td> <Td> sigma, σίγμα </Td> <Td> (s) </Td> <Td> (s) ~ (z) </Td> </Tr> <Tr> <Td> Τ τ </Td> <Td> tau, ταυ </Td> <Td_colspan="2"> </Td> </Tr> <Tr> <Td> Υ υ </Td> <Td> upsilon, ύψιλον </Td> <Td> (y) (yː) </Td> <Td> (i) </Td> </Tr> <Tr> <Td> Φ φ </Td> <Td> phi, φι </Td> <Td> (ph) </Td> <Td> (f) </Td> </Tr> <Tr> <Td> Χ χ </Td> <Td> chi, χι </Td> <Td> (kh) </Td> <Td> (x) ~ (ç) </Td> </Tr> <Tr> <Td> Ψ ψ </Td> <Td> psi, ψι </Td> <Td_colspan="2"> (ps) </Td> </Tr> <Tr> <Td> Ω ω </Td> <Td> omega, ωμέγα </Td> <Td> (ɔː) </Td> <Td> (o) </Td> </Tr> </Table> </Td> </Tr>

What is the fourth letter of the greek alphabet