optional

Optional describes something that is not required and may be chosen or omitted at discretion. In everyday language, an optional item or feature can be included or left out. In grammar, optional elements are parts of a sentence that may appear or be omitted without making the sentence ungrammatical, such as certain adverbials or relative clauses.

In legal and contract contexts, optional provisions are clauses parties may elect to accept. Optional warranties, services, or riders can be added for an extra fee or for additional scope, but they are not obligatory.

In computing, optional has specific technical meanings. Optional values or types represent data that may be present or absent. Many programming languages provide constructs such as Option, Maybe, or nullable types to model omission and avoid errors from null references. Examples include Java Optional<T>, Swift Optionals, Kotlin nullable types, and Rust Option<T>. Optional parameters in programming functions are arguments that have default values, allowing callers to omit them while preserving behavior.

In software design and user interfaces, offering optional features or settings can balance customization with simplicity. Terms such as opt-in and opt-out describe user actions to enable or disable features or data collection.

Etymology and usage notes: optional comes from Latin optio, meaning choice, via Old French option, and entered English in the early modern period. The term emphasizes choice rather than obligation, though in some contexts what is optional in one setting may be mandated in another. Clear labeling helps users distinguish between required and optional elements.