Geometry is a branch of mathematics that deals with shape, size, the relative position of figures, and the properties of shapes. It emerges independently in the number of early cultures as a practical way of dealing with lengths, area and volumes.The main concern of every student about math's subject are the geometry formulas. They are used to calculate the length, perimeter, area and volume of various geometric shapes and figures. There are many geometric formulas which are related to height, width, length, radius, perimeter, area, surface area or volume and much more. In this book, I have tried to give all the definitions which are related to geometry from class one to class twelve. Some definitions are collected from different sources. I hope all the students will benefit from this book.