The term 'one-eighth portion' can be represented by the word 'octant' which is a six letter word. An octant is a one-eighth portion of a circle, or a three-dimensional object such as a sphere. It is also used to describe a three-dimensional space that is divided into eight equal parts. In astronomy, an octant is a unit of measurement used to measure angles in the sky. In mathematics, an octant is a set of points that are all the same distance from the origin.