>[!abstract] >A concept in [[Category theory|category theory]] which means that relationships that can be deduced can also be omitted. For example, if A is the sister of B, and B is the mother of C, then A is the aunt of C. > >**Example** >If an airplane's altitude at time t is _a_(_t_), and the air pressure at altitude x is _p_(_x_), then (_p_ ∘ _a_)(_t_) is the pressure around the plane at time *t* (Wikipedia, 2024). >[!note] >I like the idea of using shorthand as we climb into higher levels of abstraction. An example that comes to mind is how composite numbers are just shortcuts for prime numbers. For example, writing 8 is easier than writing 2 x 2 x 2, which itself is easier than writing 2 + 2 + 2 + 2, although both relationships can be deduced from just the number 8. >[!related] >- **North** (upstream): [[Category theory]] >- **West** (similar): — >- **East** (different): — >- **South** (downstream): —