Not quite, a crystal is a periodic structure which is defined by lattice vectors and the content of the corresponding unit cell. The pattern drawn in the linked

Not quite, a crystal is a periodic structure which is defined by lattice vectors and the content of the corresponding unit cell. The pattern drawn in the linked image does not match this definition. Imagine it like tiling a floor. In the simplest case, all tiles are the same and the unit cell is a "primitive cell". The way they are layed out gives the lattice vectors. Now if you are using two differently styled tiles (e.g. a checkerboard pattern of black and white tiles), then the unit cell is now a "conventional cell" and consists of these two tiles. The lattice vectors now point accordingly from one tile of a type to the next one of the same type (e.g. white->white). You need two vectors that do not point in exactly the same direction to be able to cover the floor in two dimensions. Remember, you have to be able to cover the plane by moving the unit cell by integer multiples of the lattice vectors if you did it correctly. Edit: this might be it: https://i.imgur.com/75ltMjb.png https://i.imgur.com/75ltMjb.png If you shift this pattern by any integer multiple of these vectors, the pattern that it comes to lay upon will look the same as the one that was shifted. Here are some additional links. https://en.wikipedia.org/wiki/Bravais_lattice https://en.wikipedia.org/wiki/Bravais_lattice https://en.wikipedia.org/wiki/Unit_cell https://en.wikipedia.org/wiki/Unit_cell