hepta-, hept-

(Greek: seven; normally used as a prefix)

hebdomad (s) (noun), hebdomads (pl)
1. A group of seven or seven days: "The hebdomads are regular features of calendars around the world."

"Monday to Sunday or Sunday to Saturday are the sequences of days in a hebdomad."

2. Etymology: the number seven, from Late Latin hebdomas; which came from Greek hebdomos, "seventh"; from hepta, "seven".
hebdomadal (heb DAHM uh duhl) (adjective), more hebdomadal, most hebdomadal
Weekly: "Any hebdomadal activity takes place, appears, or is done every week."

"Janine always tried to make time to go regularly to the hebdomadal services at her local church."

hebdomadally (adverb) (not comparable)
A reference to a calendar week: "The family members of Bill and Lorna always tried to have a hebdomadally scheduled meal so all of them could be together."
heptachord (s) (noun), heptachords (pl)
1. A system of seven sounds: "Trudy sang a heptachord composition of seven chords or tones."
3. An ancient Greek stringed instrument: "In old Grecian times, a heptachord or a lyre with seven chords was used to present music."
heptachromic adjective) (not comparable)
1. A reference to that which exhibits seven colors: "A heptachromic spectrum presents the complete range of colors into which light can be separated when it passes through a prism."
2. Pertaining to the capability of seeing all seven colors of a spectrum: "Tamika had normal heptachromic color vision."
heptad (s) (noun), heptads (pl)
1. Numbers that have a total of seven: "The days of the week come in groups of heptads."
2. A group, or groups, of seven things: "Many mothers have a constant heptad of days as they take care of their children."
heptadactylia (s) (noun), heptadactylias (pl)
The presence of seven digits on the hands or the feet: "Floyd had an abnormal heptadactylia of fingers on his left hand while the other hand had a normal pentadactylia of fingers."
heptadactylism (s) (noun), heptadactylisms (pl)
Having seven digits on a hand or a foot: "When a person has heptadactylism, then he or she has seven fingers on one or both hands, instead of the normal five fingers on each hand; and seven toes, instead of the normal five toes on one foot or on both feet."
heptadactyly (adverb), more heptadactyly, most heptadactyly
A reference to the presence of seven digits on a hand or a foot; or on both hands and/or both feet: "The parents were shocked to see that their daughter, Fay, was heptadactyly born with so many toes on both of her feet."
heptagon (s) (noun), heptagons (pl)
A geometric shape with seven angles and seven sides: "The students were learning about heptagons in their math class."
heptagonal (adjective) (not comparable)
A reference to a formation that has seven sides and seven angles: "Kyle had a heptagonal bedroom in his apartment."
heptagynous (adjective) (not comparable)
Having seven pistils (seven female reproductive parts) of flowers: "Heptagynous blossoms have seven organs (pistils) that can receive pollen and produce fruits for plants."
heptahedron (s) (noun); heptahedrons, heptahedra (pl)
Pertaining to a solid figure with seven flat sides or faces and straight edges: "A heptahedron has several different forms; in fact, heptahedra have several shapes in convex (curving or bulging outward; such as, the exterior of a sphere) and concave (curved like the inner surface of a sphere)."
heptahydrate (s) (nouns), heptahydrates (pl)
A chemical compound that contains seven molecules of water: "Magnesium sulfate is one example of a heptahydrate."
heptamerous (adjective)
1. Plants that have flowers in groups of seven whorls or circles around stems: "There are heptamerous plant parts; such as, petals or sepals."
2. Having parts that are arranged in groups of seven: "There are some other heptamerous elements, all of which are divided into seven parts."