Character, syllable, word and sentence counts, as well as characters and syllables per word and words per sentence can determine the readability of your content by specific audiences. Since scoring systems produce numbers, it's easy for search engines to include such parameters in their algorithms and thus boost or penalize your site in the SERPs.
Rank Ranger's unique On-Page Readability Test analyzes page content using 6 respected tests, and offers support for many languages.