The 13th of October was International Plain Language Day.
Although plain language and easy-to-read language have many common features, they are different things. Plain language is clear English for everyone, whereas easy-to-read language is for groups with special reading and writing difficulties. Such groups may be elderly people, immigrants, or people with various physical conditions.
In everyday speech, plain language and easy-to-read language are often used as synonyms. The translation of these terms also causes problems. In Finnish, plain language is selkeä kieli and easy-to-read is selkokieli, in Swedish the terms are klarspråk and lättläst språk.
Both formats, plain and easy-to-read, advise you to write in a concrete way (Matti fixes the dishwasher) and avoid abstract expressions (Kitchen equipment is repaired by maintenance personnel). Common short words and light sentences are hallmarks of easy language.
It has been estimated that about 10 percent of readers need easy-to-read language; 100 percent benefit from plain language.