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OCaml records are named-field tuples — like structs but immutable by default.

type person = {
    name : string;
    age : int;
}

let ada = { name = "Ada"; age = 36 }

let () = print_endline ada.name        (* "Ada" *)

Record update — return a new record with one field changed:

let older = { ada with age = 37 }

Pattern match on records:

let describe = function
    | { name; age } when age >= 65 -> Printf.sprintf "%s, retired" name
    | { name = "Admin"; _ } -> "administrator"
    | { name; _ } -> name

The _ pattern says "ignore the rest of the fields."

Mutable fields with mutable keyword:

type counter = { mutable count : int }

let c = { count = 0 }
c.count <- c.count + 1     (* mutation: <- *)

Functional record update is preferred unless mutation is essential. For occasional mutable state, mutable fields are fine; for serious mutation, use ref (next).

Record disambiguation — when two record types share field names, OCaml uses the first matching type. Annotate explicitly when needed:

let p : person = { name = "Ada"; age = 36 }