dislocation

https://doi.org/10.1351/goldbook.09471
Defect, or irregularity, within an ordered structure.
Notes:
  1. A screw dislocation is a structure in which a helical path is traced around a linear defect (dislocation line) by the atomic planes in the crystal lattice.
  2. An edge dislocation is a defect where an extra half-plane of atoms is introduced mid-way through the crystal.
  3. In the context of lithography, a dislocation may be found in a block copolymer pattern.
Source:
PAC, 2020, 92, 1861. 'Terminology of polymers in advanced lithography (IUPAC Recommendations 2020)' on page 1871 (https://doi.org/10.1515/pac-2018-1215)