A lattice can refer to different things depending on the context. Here are some definitions:

• In mathematics, a lattice is an abstract structure studied in the subdisciplines of order theory and abstract algebra. It consists of a partially ordered set in which every pair of elements has a unique supremum and a unique infimum).
• In crystallography, a lattice is an ordered array of points describing the arrangement of particles that form a crystal. The unit cell of a crystal is defined by the lattice points. The lattice constants are the lengths and the angles between the edges of the unit cell. Crystalline materials fit into one of fourteen recognized lattice arrangements, known as Bravais lattices.
• In architecture and design, a lattice is a framework or structure of crossed wood or metal strips, or a window, door, or gate having a lattice. It can also refer to a network or design resembling a lattice.

In summary, a lattice can refer to a mathematical structure, a crystal structure, or an ornamental framework or design.