The term fool is a qualifying adjective that is used frequently when one wants to realize that someone is unintelligent, clumsy, or stands out for irrelevant behavior.
Although, on the other hand, the word is often used to refer to the person who annoys others both by doing and talking nonsense.
Likewise, it is frequently used as synonym of the word foolMeanwhile, when it is used in this sense, it is usually done in different situations, in some with the literal intention of the word and in others with an intention less related to the literal, which somehow softens its meaning.
And also, in some situations, the word is often used as insult with the clear intention of assaulting a person.
Imbécil is a word widely used at the behest of everyday and current language in many Spanish-speaking countries, because as we said it is usually expressed in situations of anger against someone who is manifesting in an annoying way towards us, that is, in informal contexts, already that in more formal contexts the use of the word to refer to someone is not well seen, even when that person is doing or saying silly things; The cause of this is found in that as the term is closely related to that of stupid and idiot and as is known, that of idiot is a pathology that is used to clinically define those who suffer from mental retardation.
In these cases it is preferable to use expressions such as: you are rambling, you do not know what you are saying, instead of using the term that can be offensive and highly uncomfortable in a formal setting.