International
Tables for Crystallography Volume A Spacegroup symmetry Edited by Th. Hahn © International Union of Crystallography 2006 
International Tables for Crystallography (2006). Vol. A, ch. 1.4, pp. 711
https://doi.org/10.1107/97809553602060000503 Chapter 1.4. Graphical symbols for symmetry elements in one, two and three dimensions^{a}Institut für Kristallographie, RheinischWestfälische Technische Hochschule, Aachen, Germany This chapter lists the graphical symbols for symmetry elements used throughout this volume. The lists are accompanied by notes and crossreferences to recent IUCr nomenclature reports. 
1.4.1. Symmetry planes normal to the plane of projection (three dimensions) and symmetry lines in the plane of the figure (two dimensions)
^{†}For further explanations of the `double' glide plane e see Note (iv) below and Note (x)
in Section 1.3.2
.
^{‡}Glide planes d occur only in orthorhombic F space groups, in tetragonal I space groups, and in cubic I and F space groups. They always occur in pairs with alternating glide vectors, for instance and . The second power of a glide reflection d is a centring vector. 
^{†}The symbols are given at the upper left corner of the spacegroup diagrams. A fraction h attached to a symbol indicates two symmetry planes with `heights' h and above the plane of projection; e.g. stands for and . No fraction means and (cf. Section 2.2.6
).
^{‡}For further explanations of the `double' glide plane e see Note (iv) below and Note (x) in Section 1.3.2 . ^{§}Glide planes d occur only in orthorhombic F space groups, in tetragonal I space groups, and in cubic I and F space groups. They always occur in pairs with alternating glide vectors, for instance and . The second power of a glide reflection d is a centring vector. 
1.4.3. Symmetry planes inclined to the plane of projection (in cubic space groups of classes and only)
^{†}The symbols represent orthographic projections. In the cubic spacegroup diagrams, complete orthographic projections of the symmetry elements around highsymmetry points, such as ; ; , are given as `inserts'.
^{‡}For further explanations of the `double' glide plane e see Note (iv) below and Note (x) in Section 1.3.2 . ^{§}In the space groups (216), (225) and (227), the shortest lattice translation vectors in the glide directions are or and or , respectively. ^{¶}The glide vector is half of a centring vector, i.e. one quarter of the diagonal of the conventional bodycentred cell in space groups (220) and (230). ^{††}Glide planes d occur only in orthorhombic F space groups, in tetragonal I space groups, and in cubic I and F space groups. They always occur in pairs with alternating glide vectors, for instance and . The second power of a glide reflection d is a centring vector. 
1.4.5. Symmetry axes normal to the plane of projection and symmetry points in the plane of the figure
^{†}
Notes on the `heights' h of symmetry points , , and :

^{†}The symbols for horizontal symmetry axes are given outside the unit cell of the spacegroup diagrams. Twofold axes always occur in pairs, at `heights' h and above the plane of projection; here, a fraction h attached to such a symbol indicates two axes with heights h and . No fraction stands for and . The rule of pairwise occurrence, however, is not valid for the horizontal fourfold axes in cubic space groups; here, all heights are given, including and . This applies also to the horizontal axes and the inversion points located on these axes.

^{†}The dots mark the intersection points of axes with the plane at . In some cases, the intersection points are obscured by symbols of symmetry elements with height ; examples: (203), origin choice 2; (222), origin choice 2; (223); (229); (230).

References
Internationale Tabellen zur Bestimmung von Kristallstrukturen (1935). I. Band, edited by C. Hermann. Berlin: Borntraeger. [Reprint with corrections: Ann Arbor: Edwards (1944). Abbreviated as IT (1935).]International Tables for Xray Crystallography (1952). Vol. I, edited by N. F. M. Henry & K. Lonsdale. Birmingham: Kynoch Press. [Abbreviated as IT (1952).]
Wolff, P. M. de, Billiet, Y., Donnay, J. D. H., Fischer, W., Galiulin, R. B., Glazer, A. M., Hahn, Th., Senechal, M., Shoemaker, D. P., Wondratschek, H., Wilson, A. J. C. & Abrahams, S. C. (1992). Symbols for symmetry elements and symmetry operations. Final Report of the International Union of Crystallography Adhoc Committee on the Nomenclature of Symmetry. Acta Cryst. A48, 727–732.