LAUSR

1. Literature review 1.1. Lexical diversity Lexical diversity (LD) has been defined as ‘the range of vocabulary and avoidance of repetition’ (Malvern et al., 2004). LD is still perceived as an indicator of second language (L2) writers’ writing abilities (Engber, 1995; Vo, 2019). As the illustrative indices to assess LD, the measure of textual lexical diversity (MTLD) and vocd-D are often utilised in many research studies. While MTLD is examined ‘as the mean length of sequential word strings in a text that maintains a given [type-token ratio] value’ (McCarthy & Jarvis, 2010, p. 384), vocd-D is calculated based on a series of randomly selected vocabulary. As LD can be examined in various ways and from various perspectives, researchers need to utilise multiple benchmarks, including MTLD and vocd-D, rather than a single yardstick (McCarthy & Jarvis, 2010).