Drawing on the rank-scale hypothesis of Systemic Functional Linguistics, this book explores the synergistic relationships among syntactic complexity at the sentence, clause, and group levels. It also examines how these relationships vary among academic English writers of different proficiency levels.

Viewing language as a dynamic, self-organizing, and self-regulating system, the book examines how changes in complexity at higher levels affect their constituent units. Linguistic complexity is conceptualized systematically across four dimensions: sentence, clause, group, and word. Dependency grammar is employed as an accessible, quantitative metric for complexity analysis. Through an analysis of academic texts produced by three groups of writers with varying levels of proficiency — Chinese Master's students, Chinese Doctoral students, and native English-speaking Doctoral students — the study identifies features of academic writing related to proficiency and uncovers interrelationships among the four dimensions of linguistic complexity. Based on these findings, the book proposes a synergistic model of linguistic complexity that illustrates how these dimensions interact and achieve dynamic balance in English academic writing across different proficiency levels.

This book offers valuable insights for researchers, educators, and graduate students. It provides theoretical exploration and practical guidance for teaching and assessing academic writing.