> For the complete documentation index, see [llms.txt](https://docs.snomed.org/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.snomed.org/education/snomed-ct-education-editorial-guide/readme/authoring/domain-specific-modeling/observable-entity/observable-entity-modeling/mass-vs-weight.md).
# Mass vs Weight
**This Editorial Guide is used for Education Purposes Only. It is used in the Authoring Courses and Certifications. It is based on the January 2026 Editorial Guide.**
The Property (qualifier value) hierarchy contains the following:
* 118538004 |Mass, a measure of quantity of matter (property) (qualifier value)|
* 726527001 |Weight (property) (qualifier value)|
Very rarely is the physics definition of *weight* used. When the term *weight* is used, it is most often referring to *mass* , as further demonstrated by the units of measure i.e., grams, kilograms, etc. Unless units specific to the physics definition of weight are specified using Newtons, assume that mass is implied.
To summarize, always use the *mass* qualifier value unless a concept is requested with Newton units that specifically refer to weight.
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