Hawaiian language
The language has only 12 letters (A, E, H, I, K, L, M, N, O, P, U, W). There are 13 if you count the okina. The okina is a real letter and came from some "K" sounds in old Polynesian languages. The okina is pronounced as a glottal stop, like the break in the middle of the word "Uh-oh". The okina is written as a backward apostrophe (small numeral 6 above and before a vowel).