A list of root words for English is available at EnglishLeap.com and VirtualSalt.com. EnglishLeap.com features a list of commonly used root words, their meanings and examples of words that are derived from these roots. The list is in alphabetical order.
As an example, the word “aquatic” comes from the root word “aqua,” which means water. The word “democracy” comes from the root “dem," which means people.
EnglishLeap.com also features root word quizzes and answers, tips on how to improve English vocabulary, a list of the site’s most commonly searched words and a list of 100 slang words used, as of 2015.
VirtualSalt.com provides a list of the common roots and prefixes that act as the building blocks of the English language. This site also hosts a root-word worksheet in which site visitors can test their knowledge of how roots and prefixes work. The list includes common roots and their meanings, plus word examples. For instance, the root "act" means to do or move. Common examples are the words action, react and activity.
VirtualSalt.com also features a list of more than 1,000 words designed to be used as a vocabulary builder.