Definition of "epi-" [ep•i-]

• On; upon: epiphyte. (prefix)
• Over; above: epicenter. (prefix)
• Around: epicarp. (prefix)
• Close to; near: epicalyx. (prefix)
• Besides: epiphenomenon. (prefix)

American Heritage(R) Dictionary of the English Language, Fifth Edition. Copyright (c) 2011 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.

• "The prefix epi- most often means “on” or “over”; pen, not a prefix, is from the Latin pæne, “almost.”"
• "The geophysicist Joseph D. Sides adds, “Writers should be advised that epi- no more intensifies the meaning of center than does pen- intensify the meaning of ultimate.”"
• "The location below the center of a nuclear detonation is, strictly speaking, the hypocenter, with the Greek hypo- meaning “under”; that word was soon overtaken by epicenter the Greek prefix epi- means “on, over”, the outbreaking point on the earth’s surface above the focus of an earthquake."