Branch of stratigraphy linked to the concept of time. In chronostratigraphy, intervals of geologic time are referred to as chronomeres. These may be of unequal duration. Intervals of geologic time are given formal names and grouped within a Chronomeric Standard hierarchy. The formal terms are: eon, era, period, epoch, age, and chron. The last four of these are the equivalent of system, series, stage, and chronozone in the Stratomeric Standard hierarchy. The formal terms are often written with initial capital letters when accompanied by the proper names of the intervals to which they refer. Some geologists hold that the term ‘chronostratigraphy’ is synonymous with ‘biostratigraphy’, but most agree that the two branches are separate.