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.
Use "heptagon" in a sentence
"It is seven-sided, a heptagon, composed of an infinitely recursive single line."
"Euclid was able to draw an equilateral triangle, square, pentagon and hexagon, but recall that the heptagon (which has seven sides) and the nonagon (nine) eluded him."
"The heptagon seven sides, for example, cannot be constructed with a compass and straightedge."