Rust ownership, borrowing, and lifetime system from the Nomicon. Covers references and aliasing rules, borrow checker mechanics, lifetime regions and scope desugaring, lifetime elision rules, subtyping and variance (covariant/contravariant/invariant), Higher-Rank Trait Bounds (HRTB), unbounded lifetimes, drop check, PhantomData patterns, borrow splitting, and lifetime mismatch limits. Use when writing, reviewing, or debugging Rust code involving ownership and lifetimes: (1) Fixing borrow checker errors, (2) Understanding why a reference outlives its referent, (3) Debugging aliased mutable reference errors, (4) Understanding lifetime elision rules, (5) Working with subtyping and variance in generic types, (6) Using PhantomData for correct variance, (7) Splitting borrows on structs/slices, (8) Understanding drop check and destructors, (9) Using Higher-Rank Trait Bounds with closures, (10) Fixing lifetime mismatch limitations.