Our most common use of the word heretic is to designate one who proposes or holds opinions that contrast with orthodoxy or with all those ideas that are considered absolute and unquestionable in a given social context or in what a religion proposes.
In the specific case of religion, an individual who, despite belonging to a certain religion in a practical way, questions it in some aspect, either expressing a criticism or questioning some precept that it proposes, will be called a heretic.
When a person is part of a social group or professes a certain religious belief, they will be required, as a basic condition of that membership, to commit to respecting all those ideas, dogmas or beliefs that they hold. Meanwhile, when this does not occur, that is, the person opines in a manner contrary to some postulates, then, he will be singled out as a heretic for that situation.
At present it is a practice that fortunately has been largely banished, however, in the past, it turned out to be very common for those who professed a different religious, social or political idea to be cruelly persecuted. Furthermore, those persecutions that were carried out were usually violent and could even end with the murder of the one or those who demonstrated contrary to the proposed order. In the mildest cases the person was excommunicated, but in the most virulent they were tortured to death, in many cases.
In the Christian religion, to cite one example, it was certainly common for those who dared to speak out against the dogmas held by the Catholic Church to be persecuted and killed.
One of the most notorious cases in the history of the Catholic Church that are considered heresy was that of Protestantism, when Christian groups back in the 16th century separated from the Catholic Church after openly criticizing many of its dogmas.
We also give this word a rather colloquial use in those cases in which we want to express that a person behaves in an absolutely insolent and daring way. This child is a heretic he cannot insult his parents like that.
