accidental

Accidental is an adjective describing something that happens by chance rather than as a result of planning or intention. It can refer to events, outcomes, or traits that are not part of the essential design of a situation. In philosophy and logic, an accidental property is a characteristic a thing may have without altering its essential nature. The noun form “accident” is more commonly used for an unplanned or harmful event. The word derives from Latin accidentalis, from accidere, to happen.

In music theory, an accidental is a symbol placed before a note to alter its pitch for the duration of the measure. Common accidentals include sharp, flat, and natural signs, with double sharps and double flats used for larger pitch changes. Accidentals apply within the current measure and are independent of the key signature. They are typically canceled at the end of the measure, returning the pitch to what the key signature or previous context dictates. Courtesy accidentals may be included to remind performers of the intended pitch or harmony.

Beyond general language and music, the term appears in philosophy to distinguish essential properties from accidental ones—traits a thing can have without changing what it is. In other fields, “accidental” can describe events or outcomes that arise without intention, often highlighting the role of chance, luck, or unforeseen factors in a process or result. Overall, accidental denotes the non-essential or unplanned element across different domains.