Printed jazz music often uses chord symbols to indicate the music’s underlying harmony. As with the Roman numeral system used in classical music theory, jazz chord symbols may be used as a tool for analysis. But they are also used for performance, like Baroque figured bass notation, with the musicians using the symbols as a framework for improvising melodies and/or accompaniments. In jazz, the symbols are generally non-specific with respect to inversion, and players of chord-capable instruments (such as piano or guitar) in jazz are accustomed to making independent choices about inversion and voicing. Depending on the situation, printed jazz music may include written notes only, or notes plus chord symbols, or even chord symbols alone.
Simple major triads aren’t common in most “modern” (post-1940) jazz. But in the rare cases that they do appear, they are indicated with a single note name:
The letter “C” above the staff is the chord symbol. The notes shown on the staff here are the corresponding pitch classes, stacked in root position in the thirds familiar to students of classical theory, though a jazz musician, composer, or arranger would rarely voice a chord in this way.
Almost always, there should some variety of seventh specified, using the numeral 7 (and when it isn’t specified, it is often implied). By convention, using the 7 alone with a note name indicates the lowered seventh: