Addressable audience
An addressable audience is a group that can actually be targeted through available platform signals - demographics, interests, behaviours, intent, customer lists or lookalikes - as opposed to a strategic audience described in research terms that no platform can select.
In practice
The gap between strategic and addressable audiences is where many plans quietly fail: the deck describes 'ambitious mid-career switchers' and the campaign buys 25-44 broad.
Good planning documents the translation explicitly, including where the proxy is imperfect and what that means for creative and measurement.