Suggest an editImprove this articleRefine the answer for “What is derived state?”. Your changes go to moderation before they’re published.Approval requiredContentWhat you’re changing🇺🇸EN🇺🇦UAPreviewTitle (EN)Short answer (EN)**Derived state** is state that is computed from other state, rather than being stored separately. **Key point:** derived state is "smart" state that does not live on its own, but automatically follows the underlying data.Shown above the full answer for quick recall.Answer (EN)Image**Derived state** is state that is **computed from other state**, rather than being stored separately. --- ### A simple example: You have a list of products: ```ts products = signal<Product[]>([]); ``` And `derived state` is, for example, the filtered products: ```ts filtered = computed(() => products().filter(p => p.inStock)); ``` You **don't store** `filtered` **manually** - you just say: "Take `products`, process it, and here's the result". --- ### Why it's needed: - **No data duplication** - Everything is always **current and in sync** - No need to update manually with every change --- ### Where it's used: - `computed()` in signals - `map()`/`combineLatest()` in RxJS - `selectors` in NgRx --- **Conclusion:** Derived state is **"smart" state** that doesn't live on its own, but **automatically follows the underlying data**. You don't manage it manually - it just "happens".For the reviewerNote to the moderator (optional)Visible only to the moderator. Helps review go faster.