Fix a basis for so that we may describe its vectors as coordinate triples (with respect to that basis). A one-dimensional vector subspace consists of a non-zero vector and all of its scalar multiples. The non-zero scalar multiples, written as coordinate triples, are the homogeneous coordinates of the given point, called "point coordinates". With respect to this basis, the solution space of a single linear equation } is a two-dimensional subspace of , and hence a line of . This line may be denoted by "line coordinates" , which are also homogeneous coordinates since non-zero scalar multiples would give the same line. Other notations are also widely used. Point coordinates may be written as column vectors, T, with colons, , or with a subscript, . Correspondingly, line coordinates may be written as row vectors, , with colons, or with a subscript, . Other variations are also possible.