Temporary phone number

A number used for a short period, from minutes (one verification) to weeks (a rental), then returned to the pool.

A temporary number is defined by its lifespan, not its technology. In SMS verification the common form is a number allocated for one activation window of a few minutes; rentals extend that to days or weeks for accounts that need repeated codes.

The practical rule: use a temporary number for the one-time gate, and move the account's long-term security to email plus an authenticator app immediately after.