What are a few Greek root words and their definitions?

Some Greek root words and their definitions are "ast," which means "star," "dem," which means "people," "hydr," which is "water," "phon," for "sound" and "therm," meaning "heat." A root word is a basic word that combines with prefixes and suffixes to form new words.

Many English words are formed using root words of Greek origin, and knowing the common root words can help with understanding the meaning of unfamiliar words. For example, the root "ast" is used to form words like "asterisk," "astronomy" and "disaster," while the root "phon" is used to form words such as "phonograph," "symphony," "phonetics" and "telephone."