What is the difference between ownership, borrowing, and references in Rust?

Question

Accepted Answer

**Ownership** — one owner. **Borrowing** — temporary access. **References** — borrowed values.

**Ownership:**
- One owner per value.
- Moved or copied.
- Dropped when out of scope.

```rust
let s1 = String::from("hello");
let s2 = s1;  // Ownership moved
```

**Borrowing:**
- Temporary access.
- References (&).
- Multiple immutable or one mutable.

```rust
let s1 = String::from("hello");
let len = calculate_length(&s1);  // Borrow
```

**References:**
- Immutable (&T).
- Mutable (&mut T).
- Must always be valid.

```rust
// Immutable reference
let r = &s1;

// Mutable reference
let r2 = &mut s1;
```

**Key differences:**
- **Ownership** — one owner.
- **Borrowing** — temporary access.
- **References** — borrowed values.

Rust: What is the difference between ownership, borrowing, and references in Rust?