Break indices are labels indicating degree of prosodic association between two sequential units on the word tier. They are markers which show the prosodic grouping of words at various levels. These are subjective values --- measures of perceived juncture between adjacent words --- and should therefore be labelled upon careful consideration of the sound record. In addition, they will typically have observable physical correlates, such as tonal markings (but see section 4.5 for examples of mismatch). J_ToBI currently distinguishes 4 degrees of disjuncture (on a scale from 0 (weak) to 3 (strong)) in the prosodic structure of Japanese.
All junctures (including filled pauses, cut-off words before restarts, etc.) should be assigned a break index value. The break labels should be aligned exactly with the word labels.