Would it appear natural to users for the terms in an array to be listed in some conventional order, e.g. from simple to complex, or on some spatial or chronological scale (examples below)? If so, adopt it. Another possibility is to list terms in order of their “importance” (significance)—perhaps, according to the frequency with which they appear in the literature of the domain. If there is no obviously useful sequence, list them alphabetically. Some examples follow.