This resource is an archived version of the Readability Guidelines.
New wiki is at: readabilityguidelines.myxwiki.org
Go to the Plain English page.
Recommendations
Make content clear and understandable, to open the web up for users with different literacy levels and access challenges. WCAG states that "using the clearest and simplest language appropriate is highly desirable." The United Nations recommends plain language for communications.
1. Do not use formal or long words when easy or short ones are available. Use ‘buy’ instead of ‘purchase’, ‘help’ instead of ‘assist’, and ‘about’ instead of ‘approximately’. Write for the reading comprehension of a 9 year old. This helps you reach the most users and makes your content easy to scan.
2. Jargon and buzzwords are rarely clear language. Often, these words are too general and vague and can lead to misinterpretation or empty, meaningless text. Avoid them. Instead, think about what the term actually means and describe that. Be open and specific.
Example:
"Let's touch base in 10 and do some blue sky thinking." This uses jargon.
"Let's meet in 10 minutes to think of ideas." Conveys same meaning using clear language.
3. Write conversationally – picture your audience and write as if you were talking directly to them, with the authority of someone who can help and inform.
4. Test your content with users: what is 'plain' for one person may not be for someone else.
Usability evidence
Guideline 3.1 Readable: Make text content readable and understandable., Web Content Accessibility Guidelines (WCAG) 2.0, 2008.
'Convention on the Rights of Persons with Disabilities', page 4 Article 2, Definitions, The United Nations Convention on the Rights of Persons with Disabilities, 2018.
'Plain Language Is for Everyone, Even Experts', H. Loranger, Nielsen Norman Group, 2017
'The Public Speaks: An Empirical Study of Legal Communication', C. R. Trudeau in 14 Scribes J. Leg. Writing 121 2012
'Strengthening plain language', International Plain Language Federation. Undated.
Plain Language Commission style guide, Plain Language Commission, 2011
'The principles of readability', Impact Information, William H. DuBay, 2004
Plain language entry, Wikipedia, last updated 2018
There's a few competing standards and schemes for writing in plain or clear English.
If you are in the UK the Plain English Campaign probably springs to mind, thanks to some very good PR over the years.
But there are alternative standards for writing in English (https://www.clearest.co.uk/plain-language-commission-style-guide), and an international body trying to develop a set of consistent, widely applicable standards. (http://www.iplfederation.org)
One of the real successes of Web Content Accessibility Guidelines has been its widespread adoption at the expense of alternatives. With this is mind, I don't think there's much need for us to try and branch too far into plain / clear English turf.
Many people use readability formulae to guide and assess their writing. Microsoft uses the Flesch Reading Ease Test and the Flesch-Kincaid Grade Level Test to assess the readability of a text. A guy called William H DuBay (interesting for other reasons, BTW) has written a number of books about readability which are useful. His perspective is as a technical writer but he focuses on context and doesn't have an axe to grind or particular formula to promote (he things readability formulas are useful). A lot of his work is downloadable for free on his website. The Principles of Readability for example.
This took place in Slack: https://readabilityguidelines.slack.com/messages/CDE1RGL3Z/details. Joining link: https://bit.ly/2D0OW1F Key evidence is posted on the relevant wiki Article pages.
Regarding Readability formulas, the following are not based on the US education system:
Flesch Reading Ease
CEFR Level
IELTS Level