Tacit collusion
A cartel is a formal agreement between companies to control the price of a commodity or product etc - like OPEC. Tacit collusion occurs when companies make an informal agreement to fix prices (i.e. they do this without letting their competitors or official bodies know). Your confusion might arise from the fact that members of a Cartel (an officially organised group) can still engage in unofficial agreements (tacit collusion), although it is usually firms outside a cartel who do this
Under some conditions, a person's silence after a statement is made gives rise to a legal inference that the person who remained silent gave the statement tacit approval.
tacit
The word "tacit" is an adjective.
tacit tacit
Tacit means you don't play.
Shared or Joint monopoly refers to anticompetitive behaviour by firms, normally an oligopoly, in order to secure monopoly profits for the firms as a group. Essentially, shared monopoly requires some form of collusion but stops short of being a formal cartel. It is therefore similar to tacit collusion. In a shared monopoly firms may not compete for the same customers and have instead local monopolies.
Collusion - EP - was created in 2005.
Baseball collusion happened in 1986.
Tacit Software was created in 1997.
I did that with his tacit approval.