または is a conjunction meaning 'or'. It is used to list mutually exclusive alternatives, often in formal contexts like notices, forms, or written instructions. It is more formal than か, which is common in everyday speech. For example, when giving choices in writing, you say コーヒーまたは紅茶 (coffee or tea). You cannot use it with verbs in casual speech; instead, use か for spoken Japanese.

In writing, または can also connect two full clauses: 電車で行く、またはバスで行く (go by train, or go by bus). But this sounds stiff and is rare in conversation.

Note that または is exclusive: it implies choosing one of the options, not both. If you want to say 'both A and B', use も or と.