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Short answer

Rust manages memory through ownership rules the compiler checks, with no garbage collector and no runtime cost:

1. Each value has an owner.
2. There is one owner at a time.
3. When the owner goes out of scope, the value is dropped. [S1]

fn len(s: &String) -> usize { s.len() } // borrows, caller keeps s

Claims

• id: C1 claim: Each value in Rust has an owner. source: S1 evidence: "Each value in Rust has an owner."
• id: C2 claim: There can only be one owner at a time. source: S1 evidence: "There can only be one owner at a time."
• id: C3 claim: When the owner goes out of scope, the value is dropped. source: S1 evidence: "When the owner goes out of scope, the value will be dropped."
• id: C4 claim: You can have one mutable reference or many immutable ones. source: S2 evidence: "At any given time, you can have either one mutable reference or any"

Sources

• [S1] What is Ownership? - The Rust Programming Language. The Rust Project (The Rust Programming Language book). https://doc.rust-lang.org/book/ch04-01-what-is-ownership.html . License: MIT OR Apache-2.0 (rust-lang/book). Accessed 2026-11-04.
• [S2] References and Borrowing - The Rust Programming Language. The Rust Project (The Rust Programming Language book). https://doc.rust-lang.org/book/ch04-02-references-and-borrowing.html . License: MIT OR Apache-2.0 (rust-lang/book). Accessed 2026-11-04.

License: this note is CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). Summary by iinventedlight (AI-assisted).

@misc{iil_note_c5e5w64x,
  author = {{iinventedlight}},
  title = {{Rust ownership and borrowing in five rules}},
  howpublished = {iinventedlight Library},
  year = {2026},
  date = {2026-11-04},
  url = {https://iinventedlight.com/library/notes/rust-ownership-borrowing/},
  note = {Permanent ID iil:note:c5e5w64x. License: CC-BY-4.0.},
}

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