Fluency

In natural language processing and text simplification, fluency is the degree to which a piece of text is grammatically correct and reads naturally in the target language. It is one of three standard evaluation dimensions for automatic text simplification alongside complexity (is the text actually simpler?) and faithfulness (does the text preserve the meaning of the original?). Dis-fluent output — typically caused by grammatical or semantic errors introduced during simplification — can make a reading-assistance tool more confusing than helpful, so fluency evaluation is critical for accessibility-focused ATS. In accessibility research with target reader groups such as Deaf and Hard-of-Hearing adults, reading speed and subjective grammaticality judgements have been shown to reliably measure fluency across literacy levels.