fourth
the fourth estate the press; the profession of journalism.
☞ The three traditional Estates of the Realm (the Crown, the House of Lords, and the House of Commons) are now viewed as having been joined by the press, which is regarded as having equal power. As early as 1843 Lord Macaulay stated: 'The gallery in which the reporters sit has become a fourth estate of the realm'.
the fourth wall
1 the space which separates a performer or performance from an audience.
2 the conceptual barrier between any fictional work and its viewers or readers.