pentacle (a five-pointed star formed by five straight lines connecting the vertices of a pentagon and enclosing another pentagon in the completed figure)
pentad (a group of five)
pentadactyl (having five fingers or toes on each hand or foot)
pentagon (a polygon having five sides and five interior angles)
pentagram (a five-pointed star formed by five straight lines connecting the vertices of a pentagon and enclosing another pentagon in the completed figure)
pentahedron (a solid having five plane faces)
pentameter (a line of verse consisting of five metrical feet)
pentapeptide (a polypeptide composed of five amino acids)
pentaploid (having five haploid sets of chromosomes)
pentarchy (government by five rulers)
pentastich (a poem or stanza having five lines)
Pentateuch (the first five books of the Hebrew Scriptures)
pentathlon (an athletic contest in which each participant competes in five track and field events, usually sprinting, hurdling, long jumping, and discus and javelin throwing)
pentatonic (of or using only five tones, especially the first, second, third, fifth, and sixth tones of a diatonic scale)
pentavalent (having a valence of five)
pentoxide (a compound having five atoms of oxygen combined with another element or radical)
Definitions are taken from:
The American Heritage® Dictionary of the English Language, Third Edition copyright © 1992 by Houghton Mifflin Company.
Electronic version licensed from InfoSoft International, Inc. All rights reserved.
Webster's Third New International Dictionary, Unabridged. Merriam-Webster, 2002.
http://unabridged.merriam-webster.com (30 Sep. 2006).
English-Word Information: Word Info about English Vocabulary (wordinfo.info).