在物理学中，内含性质（英语：intensive property）是指系统中不随系统大小或系统中物质多少而改变的物理性质，内含性质是尺度不变的物理量。

相反的，外延性质（英语：extensive property）是指系统中会和系统大小或系统中物质多少成比例改变的物理性质，二个个别独立，不相关的系统，其外延性质有加成性，个别系统外延性质的和就是总系统的外延性质。

例如，密度和物质的多少无关，因此是物质的内含性质。物质的量常用质量及体积来表示，这二个都是外延性质。

Physical properties of materials and systems can often be categorized as being either intensive or extensive quantities, according to how the property changes when the size (or extent) of the system changes. According to IUPAC, an intensive property is one whose magnitude is independent of the size of the system. An extensive property is one whose magnitude is additive for subsystems.