Move to 2NF: Ensure that all non-key attributes are fully functionally dependent?

Short answer: on the primary key. Remove partial dependencies (when a non-key attribute depends on part of a composite key).

Real-world example (ShopNest)

Product and Category are separate tables (normalized). The order line stores product id + price snapshot—not a giant duplicated product blob.

Say this in the interview

1. Define — one clear sentence (the short answer above).
2. Example — relate it to a project like ShopNest or your real work.
3. Trade-off — when you would not use it.