Spatial dimensions for an animal
Wikipedia has a quite didactic article on this: https://en.wikipedia.org/wiki/Anatomical_terms_of_location#Axes

These terms are complementary with a mathematical coordinate system: if you are describing a system of axis for a cylinder, you will need to specify that (e.g.) $z$ is along its symmetry axis, here you will say that $z$ is along the rostro-caudal (or antero-posterior) axis. Also, in biology, axes do not have to be straight lines, see the neuraxis: