Plain language is clear and avoids complex words. It is easy to read, understand, and act upon after just one reading.
These are the main traits of plain English:
Use of commonly understood words
Use of the fewest words necessary
Sentences are up to 15-20 words
Paragraphs have up to 6-8 lines
To achieve plain writing, one must watch for:
Prepositions
Superlatives
Wordy phrases (e.g., passive voice)
Simple, shorter sentences highlight key ideas. Subject + Verb + Object phrases work best. Reading aloud helps detect unclear and poor wording.
The goal of plain language is to produce texts that are concise and have a clear purpose. One must avoid:
Multisyllabic words
Cliches
Business jargon
Vague words
Plain writing is not only about words and tone. It also involves using easy-to-read designs. That may include using bullet points and internal headings.
READ: Why use plain English?
Readability checkers like the Gunning Fox Index help define how easy it is to read a text. Texts aimed at the general public have a fog index of less than 12. An index of 8 or less is vital to reach an even wider audience.
When I first drafted this post, the fog index was 11. Since my goal was to use plain writing, I scored 7 after revision.
To sum it up, plain language:
Has a clear goal
Must answer questions
Omits unneeded details
Has a positive and conversational tone
Is easy to read
Uses proper grammar and spelling
If you want to learn more, check the course Writing in Plain English.