In geometry, a three-dimensional space is a mathematical space in which three values (coordinates) are required to determine the position of a point. Most commonly, it is the three-dimensional Euclidean space, the Euclidean n-space of dimension n=3 that models physical space. Everything around us, from the houses we live in to the objects we use in everyday life, has three dimensions: height, length, and width. Three-dimensional shapes have height, which is the same as thickness or depth. In addition to the three dimensions of space, time is often considered as a fourth dimension. However, some theories suggest that there may be more than three dimensions, such as string theory, which suggests that six more dimensions exist but are somehow hidden from our senses.