Dissertation (MSc Mathematics)The sudy of a language is very important for the cryptanalysis of substitution and/ or permutation ciphers. In that type of ciphers one letter is substituted by another one, or its order is changed with the order of another letter also from the text. In either case the ―personality‖of the alphabets remains intact, hidden inside a different vest, but intact anyway. If it is true that the morden block ciphers hide those characteristics, given the fact that they operate at bit level, we think that it is still important to have at hand such a tool for our own laguage, we can think more as an education tool, in order to present and/ or study the classical ciphers. We also have one more tool in our cryptanalyst toolbox. In this dissertation we present the statistical analysis of letters frequencies in Swahili language; we have discussed the mostly frequent letter in the Arabic language as well as in the English language. We also discussed the Swahili alphabets and analyse some Swahili articles and present the frequencies of the letters as used in the Swahili language. Lastly, we present the use of t-test and provide the level of confident interval for each letter.