There is some confusion in terms with respect to the labelling of four-dimensional phenomena. The confusion centers around the four-dimensional analog of the cube. There are basically two camps. The first camp uses the hyper- prefix for only the fourth dimension, and the word 'tesseract' to refer to one of two things - either the four-dimensional hypercube folded out into three-dimensional space, or to the cube-inside-a-cube visualization of the four-dimensional hypercube. The second camp uses the hyper- prefix to refer to any dimension above the third (and sometimes to refer to any dimension), and 'tesseract' to refer to a four-dimensional hypercube. I have decided to adopt the second convention - throughout this page I refer to four-dimensional hypercubes as tesseracts.