The word accident has its origin in the Latin term accidens. The concept refers to something that happens or arises unexpectedly, since it is not part of the natural or essential of the thing in question.
The most frequent use of the term is linked to the event that happens without intention and that causes damage to a living being or to a thing. For example: “Two people died in a traffic accident on Route 8”, “The young woman remains hospitalized after falling from the balcony by accident”, “I accidentally cut myself while preparing food”.
As noted by Digopaul, accidents can happen for different reasons and have very different consequences. While a plane crash can kill hundreds of people, a plastic cup that falls by accident will not cause major inconvenience.
Accidents can be classified in different ways depending on where they occur. In this way one can talk about home accidents (such as an oil burn in the kitchen), traffic accidents (two cars colliding on the street) or work accidents (a construction worker who trips and falls from scaffolding). This last meaningit gives rise to a lot of controversy in the business field, since the hiring in black supposes the absence of a work risk insurance. Thanks to disinformation, the best friend of the exploiters, millions of employees do not know that an accident at work is considered to be one that occurs both while they are on the job and during the trip to and from the office and back home.
It is common in some regions to confuse the term with incident, but there are clear differences between the two. We can think of an incident as a fact that “cuts” reality and alters the course of things. An unexpected event, yes, but that does not represent a misfortune or the destruction of something, but possibly brings about a change of decisions.
A geographical accident, on the other hand, is an elevation, a depression or another type of irregularity that can be noticed in a terrain. Some examples are the cliffs, gulfs, mountains, valleys and blue holes.
Accidents also appear in grammar and music. In the first case, they indicate modifications of words according to time, gender or number, allowing coherence in the sentences. The Castilian words that are affected by these changes are adjectives, nouns, verbs, pronouns and articles. These alterations can affect its structure, its way or even its meaning.
In music, on the other hand, accidents enrich a melody since they allow different tones to be combined through momentary alterations. To give a didactic example, if we are composing a piece in C major for piano, in principle we can only play the white keys, which correspond to the sounds allowed within the mentioned scale. However, one of the keys related to DO is SOL major, which contains one of the black keys (the sharp F). So, if we wanted part of the work to go through a major SOL moment, every time we wrote an F in that section, we should clarify that it is sustained. This, in the eyes of a musician, is an accident.
In our language, the noun in question also has a very derogatory and dangerous use for the psychology of a person: children who are conceived by accident. Given the high rate of unexpected pregnancies, especially in adolescents, millions of people carry this terrible label of unwanted child on their foreheads.
But all the nuances that this word gives to sentences are not necessarily negative or tragic. It is said, for example, that someone accidentally heard something, meaning that they did it unintentionally. While the information you accessed may be something terrible for that person, it could also be plans for a surprise party or a marriage proposal. It will be up to everyone to judge these last two news items and decide whether or not they have a happy or dismal character.