Without proper linguistic competence in English language, academic writing is one of the most challenging tasks, especially, in various genre specific disciplines by L2 novice writers. This paper examines the role of diction and expression through error analysis in English language of L2 novice writers' academic writing in interdisciplinary texts of IT & Computer sciences and Business & Management sciences. Though the importance of vocabulary in L2 academic discourse is widely recognized, there has been little research focusing on diction and expression at higher education level. A corpus of 40 introductions of the published research articles, downloaded from the journals (e.g., 20 from IT & Computer sciences and 20 Business & Management sciences) authored by L2 novice writers, was analyzed to determine lexico-grammatical errors from the texts by applying Markin4 method of Error Analysis. "Rewrites" in italics letters is an attempt to demonstrate English language flexibility, infinite vastness and richness in diction and expression, comparing it with the excerpts taken from the corpus.