The adjective tacit comes from Latin, more specifically from tacitus, which means silent. In relation to its meaning, it is what is not said because it is unnecessary. In this way, if two people reach a wordless pact, a tacit agreement takes place.
Words are not always necessary for understanding
Although words are the fundamental element of communication, they are not always essential for a good understanding. In fact, in certain contexts of language, messages are implied, that is, they are hidden because they do not appear, but that does not mean that they are not present. In this way, two people who know each other very well can understand each other through a simple look and their communication is done without words and tacitly. Tacitus
The tacit agreement turns out to be an unwritten pact in which the people involved commit themselves and in their commitment it is not necessary to sign or say anything. Let’s look at two typical situations:
1) Two people close a deal verbally and at the end of the meeting they hold hands as a sign of compliance. With this gesture, they sign a commitment of obligation to fulfill;
2) An individual lends an object of value to another person and at no time mention the fact that the object must be returned later.
Although the tacit pact is a very socially risky mechanism, in most formal agreements it is convenient to have an element that obliges the pact to be fulfilled (usually this element is a contract). Tacitus
Tacit or hidden subject
From a grammatical point of view, in some language contexts it is not necessary to use the subject. This happens when it is understood who is the subject who carries out the action and, therefore, it is unnecessary to mention him. In the sentence “I won the game” the subject is “I”, but it is not essential to use it because the verbal form already indicates who it is. In the phrase “the other day you won the game” the tacit subject is you. And in the prayer “they played in the backyard” they are the hidden subjects. Tacitus
Certain events are evident, but nevertheless they cannot be explained with words. When this happens, we speak of tacit knowledge. In this sense, we identify a person’s voice or recognize their face by an automatic mental process, so we don’t know how to explain how to do it, but we do.