Apparent authority is the power held by an agent or other actor to affect a principal's legal relations with third parties when a third party reasonably believes the actor has authority to act on behalf of the principal and that belief is traceable to the principal's manifestations.

See Watteau v. Fenwick (Q.B. 1893)

The owner of a beerhouse left his manager in charge and forbade him, privately, to buy cigars on credit. The manager bought cigars on credit. The owner was held liable: the supplier dealt with the man who ran the house, doing what men who run such houses ordinarily do. Secret instructions bound the manager — they did not bind the world.

What matters is not what you told your agent, but what the wharf, the market, and your suppliers reasonably believe from what you have let them see: his title, his station, your silence. A private limit, unknown to those he deals with, protects you not at all. If you would cut down an agent's apparent authority, the world must be told.

A note on labels

Watteau is often taught as inherent agency power — a residual doctrine binding the principal for acts usual to an agent's position even where actual and apparent authority both fail. The Third Restatement disfavors the label, folding such cases into apparent authority and estoppel; your casebook may keep all three lenses on the shelf. However labeled, the holding stands: private limits, unknown to those who deal with the agent, do not travel.