Sentence Length
Shorter sentences improve readability and understanding. Sentences should as a rule of thumb not contain more than 20 words. Each sentence should deal with one subject only.
Sentence length exceeds allowed sentence length.
The number of words in a sentence exceeds the allowed number of words defined by a rule. There are two rules that can be activated by an Author: The rule on Specification level defines the sentence length for plain text, while the rule on Requirements level defines the sentence length for requirements.