This corpus-based study explores the syntactic complexity of adapted Czech texts designed for learners of Czech as a second language (L2). It investigates how syntactic complexity varies according to learner proficiency levels (A2, B1, B2) as defined by the Common European Framework of Reference for Languages (CEFR) and how these adapted texts differ from their original versions. Quantitative analyses using metrics such as average sentence length (ASL), average clause length (ACL), mean dependency distance (MDD), and mean hierarchical distance (MHD) demonstrate clear systematic simplifications in adapted texts at lower proficiency levels. At A2 and B1 levels, adapted texts were found to be significantly less syntactically complex compared to their original counterparts. However, these differences diminished notably at the B2 proficiency level, indicating a gradual alignment of adapted texts with native-level syntactic complexity as learner proficiency increased. These results underscore the importance of careful syntactic calibration in creating educational materials for language learners, highlighting implications for curriculum design, instructional methodologies, and materials development. The findings offer valuable insights for language educators and textbook authors aiming to optimize reading materials to support language acquisition effectively

This study investigates the length distributions of syntactic units in Czech across multiple hierarchical levels: sentences, independent clauses, clauses, phrases, subphrases, and chunks. Using a diverse dataset – including Universal Dependency treebanks, presidential speeches, the Czech Bible, and random sample from corpora of modern Czech – the analysis examines whether lengths of these syntactic units follow consistent distributional patterns. Length is defined as the number of immediate subunits, and the distributions were modeled using the hyper-Poisson distribution. The results demonstrate that the hyper-Poisson model fits well distributions of length of all abovementioned syntactic units, pointing to a common principle underlying the organization of syntactic structure in Czech.