Size

Within the context of the GTS community (and also of the SD community), size becomes a measure of length (one-dimensional space).

In the case of humans (or anthropomorphic beings), their size is conventionally the distance between the soles of the feet and the upper extremity of the head while standing up, that is, its height or stature.

And if it is a question of other objects of non-anthropomorphic aspect, then it would have to define its size based on the distance of 2 different points of its volume.