Expressive Notation

This is used even when perfect expressivity is impossible, even though it is common in the literature to warn against using only partially expressive notation. I would note that the two-letter codes for US states

employed by the US Post office have proved highly useful because they are mostly expressive: states with two-word names are symbolized by the first letters of each word, and most other states by either the first two

letters or the first and last. The utility of this system is not erased by the fact that Missouri has to be symbolized by MO (because there are several states starting with MI), though the occasional Missouri-bound letter is likely sent to Michigan by mistake.