“…In ARA, researchers often utilize various linguistic features to quantify the difficulty level of a text (Flesch 1948;Chall 1948). These features can capture different aspects of the linguistic nature of a text, including vocabulary, syntax, semantics, and discourse structures (Dell'Orletta, Montemagni, and Venturi 2011;Hancke, Vajjala, and Meurers 2012;Sung et al 2015;Denning, Pera, and Ng 2016;Arfé, Mason, and Fajardo 2018;Jiang et al 2019). Due to the richness of linguistic features, they are incorporated in both traditional machine learning and modern deep learning approaches.…”