The prefix omni- means “all.” It comes from the Latin word omnis, also meaning “all.” Because the meaning of omni- is so clear and easily recognizable, the prefix has long been used in English to make new words. For example, the meanings of words such as omnipurpose (“all-purpose”) and omnitolerant (“tolerant of all things”) are easy to guess, even without a definition. Omni- can be compared to the prefix pan-, which also means “all.” Pan-, however, comes from Greek and is most commonly used in English in compounds with names of nationalities: Pan-American.
