Heptadic

Part of speech: adjective

Definitions

1. Characterized by the presence of seven members or elements, such as in a group or set
2. relating to or composed of seven units, often seen in classifications or systems
3. denoting a structure or pattern that is arranged in groups of seven for specific purposes

Etymology: "Heptadic" is simply "heptad" with the adjectival ending "-ic" added, so its meaning follows directly from the parts. The "heptad" half comes from Greek "heptas," meaning a group of seven or the number seven, which gave English a noun for a set of seven things. Adding "-ic" turns that noun into a description of anything belonging to or relating to such a set of seven. The "-ic" ending itself has a long journey. It descends from Greek "-ikos," passed into Latin as "-icus," and reached English through Old French "-ique" and Middle English "-ik," before settling into its modern form. Because it is one of the most productive adjective endings in English, it can be attached to nearly any noun from a classical base, which is why it appears on so many technical words built from numbers and patterns.

Synonyms: sevenfold, septenary

Antonyms: nonadic, eightfold