Why has it been difficult to create one definition that fits every style of jazz?

Creating a precise, all-encompassing definition of jazz is considered futile because the music is a constantly evolving, expanding art form that has passed through numerous distinctive phases since the turn of the 20th century. A definition that accurately describes one style, such as New Orleans style or swing, often becomes inappropriate when applied to later developments like free jazz.1

Historically, attempts to define jazz by specific traits have proven restrictive or inaccurate:
* Improvisation: While central to the genre, jazz has always relied on a mix of composition, arrangement, and ensemble work, making it neither entirely predetermined nor entirely extemporized.1
* Syncopation and Swing: Once considered essential, these elements are absent in much authentic jazz, and musicians have demonstrated that "swing" can be generated without syncopation.1

Ultimately, jazz is a "composite matrix" of diverse vernacular elements—including blues, ragtime, and hymns—that defies a single label, leading many to agree with Louis Armstrong that "if you have to ask, you’ll never know".12