Second Normal Form (2NF)
A non-key field must not be a fact about a subset of a key (no partial dependencies)
If X=A ? B is a candidate key, A does not determine Y for any non-empty A, non-empty B, and non-prime Y.
All candidate keys have 1 field ? 2NF
Example: R = (part, wh, qty, wh-addr), with FDs {part, wh} ? qty and wh ? wh-addr