This dissertation offers a comprehensive review of the current literature on the historical sound changes that underlie the diachronic development of the Armenian sounds from their Proto-Indo-European origin. Additionally, it presents novel analyses of the following six phonological or morphophonological phenomena: (i) The original phonological distinction between the two Armenian historical laterals is analyzed in terms of voicing contrast. (ii) The fate of the inherited final nasals in the classical language is argued to be fully predictable based on the duration of the preceding inherited vowels. (iii) The non realization of a word final palatal glide is explained as a morphophonological process that targets specific suffixes. (iv) The non-realization of the aorist augment is analyzed as a metrically conditioned zero allomorphy. (v) The affricate dissimilation in the aorist subjunctive is interpreted with reference to the prosodically conditioned reduction of /i/ in the subjunctive suffix. Finally, (vi), modern Armenian plural allomorphy is analyzed in terms of the interaction between morphophonological REALIZATION and ALIGNMENT requirements and syllabic well-formedness in the framework of Optimality Theory (Prince and Smolensky 1993/2004).