Having just written an article about everyday uses of Geometry and another article about real world applications of the principles of Geometry, my head is spinning with all I found. Being asked what I consider the five most important concepts in the subject is "giving me pause." I spent almost my entire teaching career teaching Algebra and avoiding Geometry like the plague, because I didn't have the appreciation for its importance that I have now. Teachers who specialize in this subject may not totally agree with my choices; but I have managed to settle on just 5 and I did so by considering those everyday uses and real world applications. Certain concepts kept repeating, so they are obviously important to real life.