Point defects are defects that occur at a single lattice site in a crystal. The three main types of point defects are vacancies, interstitials, and substitutional atoms.

A vacancy defect is an empty lattice site in a crystal. It can be caused by the removal of an atom from the lattice, or by the failure of an atom to occupy a lattice site during crystal growth.

An interstitial defect is an extra atom in a lattice site in a crystal. It can be caused by the addition of an atom to the lattice, or by the movement of an atom from one lattice site to another.

A substitutional defect is an atom that has replaced another atom in a lattice site in a crystal. It can be caused by the substitution of one atom for another during crystal growth, or by the diffusion of an atom from one lattice site to another.

Line defects are defects that extend in one dimension in a crystal. The two main types of line defects are dislocations and grain boundaries.

A dislocation is a linear defect in a crystal where atoms are misaligned. It can be caused by the movement of atoms during crystal growth, or by the application of stress to a crystal.

A grain boundary is a boundary between two grains in a polycrystalline material. It is a region where the atoms are misaligned, and it can have a significant effect on the properties of the material.

Planar defects are defects that extend in two dimensions in a crystal. The two main types of planar defects are stacking faults and twin boundaries.

A stacking fault is a region of a crystal where the atoms are arranged in a different order than the rest of the crystal. It can be caused by the movement of atoms during crystal growth, or by the application of stress to a crystal.

A twin boundary is a boundary between two regions of a crystal that are mirror images of each other. It can be caused by the growth of two crystals from the same nucleus, or by the deformation of a crystal.

Defects in solids can affect the properties of materials in a number of ways. They can change the electrical conductivity, thermal conductivity, and mechanical properties of materials. They can also cause materials to be more brittle or ductile, and they can affect the color and transparency of materials.

Dislocations are line defects, not point defects.

Stacking faults are planar defects, not line defects.

Dislocations are line defects, not planar defects.

Vacancies are the most common type of point defect in solids.