Using short sentences and words with as few syllables as possible makes things easier to read.  We've developed a checker using the Flesch Reading Ease Score formula for you to perfect your copy.  It should only be used as a rough guide to how easy your copy is to read but aim for a score of 60 so that a 13-year old can read it.
A vowel in a word points to a new syllable and in this scoring method, the number of syllables makes things harder to read. However, the English language is full of exceptions to this rule.  We've tried to capture all of these but we welcome your feedback on any we may have missed.