In contemporary English, the word "necessary" is not typically used to refer to a toilet or restroom facility. However, in some older or regional dialects, "necessary" has been used as a slang term for a toilet or outhouse.

If someone were to use the term "necessary" to refer to a restroom facility in a contemporary context, it would likely be understood only by a small subset of English speakers who are familiar with this particular slang usage.

In general, it's more common to use other terms such as "restroom," "bathroom," "toilet," or "lavatory" to refer to a facility where one can relieve themselves or attend to personal hygiene. The specific term used may vary depending on the region, context, and social norms.