The paper focuses on the essential problem of religious communication analysis. It is aimed to study linguistic means representing Orthodox sermon in Modern Greek. 2000 Orthodox sermons of the 20th century in Modern Greek were analysed. The authors outline linguistic and communicative features of the Modern Greek Orthodox sermon as well as define its genre specifics. Having analysed the language of the Orthodox communication, the authors outlined two opposite processes, namely terminologisation and determinologisation of the religious lexicon. The results of the research show that the social changes in the world in the late 20th century, led to some changes in the lexicon and in the semantics of the religious discourse. In the Orthodox sermons, the figures of speech are used, highlighting the author's intention. The complex extended sentences with subordinate components, comparisons, explicitations, appellatives and quotations are typical of sermon in Greek. Although the sermon is delivered in Demotic Greek, in some ways it reflects the phonetic, morphological, structural, lexical and word-building features of Katharevousa. The sacred lexicon performs the liturgical function: it is used in written sacred texts and prayers in church. The vernacular language performs missionary function. The communicative space of the sermon is formed from the perspective of Orthodox theological worldview.