A sixth chord is a type of chord used in music theory, consisting of a triad with an added sixth note. It is often used in jazz and pop music as a way to add texture and tonal color to a song's harmony. However, there are a few synonyms for the term, including the tonic-sixth chord, the added-sixth chord, and the 6th chord. Each of these terms refers to the same chord structure, but may be used in different contexts depending on the style of music or the particular chord progression being used. Regardless of the term, the sixth chord remains a popular choice for musicians looking to add interest and complexity to their compositions.