### 12.17.7 Geometry Property Functions

[12.17.7.1 General Geometry Property Functions](gis-general-property-functions.html)
[12.17.7.2 Point Property Functions](gis-point-property-functions.html)
[12.17.7.3 LineString and MultiLineString Property Functions](gis-linestring-property-functions.html)
[12.17.7.4 Polygon and MultiPolygon Property Functions](gis-polygon-property-functions.html)
[12.17.7.5 GeometryCollection Property Functions](gis-geometrycollection-property-functions.html)

 Each function that belongs to this group takes a geometry value as its argument and returns some quantitative or qualitative property of the geometry. Some functions restrict their argument type. Such functions return `NULL` if the argument is of an incorrect geometry type. For example, the [`ST_Area()`](gis-polygon-property-functions.html#function_st-area) polygon function returns `NULL` if the object type is neither `Polygon` nor `MultiPolygon`.

