How many letters does the greek aplhabet have?

there are 24 letters in the greek alphabet. Here is a complete list :

Uppercase/Lowercase greek spelling English pronunciation

Α,α Άλφα alpha

Β,β Βήτα beta

Γ,γ Γάμα gama

Δ,δ Δέλτα delta

Ε,ε Έψιλον epsilon

Ζ,ζ Ζήτα zeta

Η,η Ήτα eta

Θ,θ Θήτα theta

Ι,ι Γιώτα iota

Κ,κ Κάπα kapa

Λ,λ Λάμδα lamda

Μ,μ Μι me

Ν,ν Νι ne

Ξ,ξ Ξι xe

Ο,ο Όμικρον omicron

Π,π Πι pe

Ρ,ρ Ρο ro

Σ,σ,ς * Σίγμα sigma

Τ,τ Τάυ taf

Υ,υ Ύπσιλον ipsilon

Φ,φ Φι phe

Χ,χ Χι he

Ψ,ψ Ψι pse

Ω,ω Ωμέγα omega

*the third character is used only when a Word ends with sigma and is pronounced :sigma teliko (ending sigma)