septm̥
“seven, the number seven”seven, seventh
Root for the number seven, yielding Latin septem, English seven, Greek hepta.
Discussion
The Proto-Indo-European word *septm̥ is the cardinal numeral "seven" and belongs to the remarkably well-preserved set of Indo-European numerals that can be traced with confidence across nearly every branch of the family. The final *-m̥ represents a syllabic nasal, a sound that developed differently in each daughter language but whose former presence is confirmed by the comparative evidence.
In Germanic, the initial *s was retained, and the medial *-pt- cluster was simplified. Old English seofon became modern English seven, with the characteristic Germanic voicing of the medial consonant. German sieben and Dutch zeven are close cognates. Grimm's Law did not affect *s, which remained unchanged, making the Germanic forms relatively transparent reflexes.
Latin septem "seven" preserves the proto-form with remarkable fidelity and is the source of September (originally the seventh month in the early Roman calendar, which began in March), septennial, and septet. The Latin numeral system was borrowed wholesale into scientific and technical English, ensuring that this root remains highly visible in modern vocabulary.
Greek hepta "seven" (with regular loss of initial s-) gave English heptagon, heptathlon, and heptarchy. Sanskrit saptá "seven" and Avestan hapta confirm the Indo-Iranian reflexes. Old Irish secht, Welsh saith, Lithuanian septyni, and Old Church Slavonic sedmĭ round out the picture across Celtic, Baltic, and Slavic.
The extraordinary consistency of the word for "seven" across all major branches is typical of the Indo-European numeral system, which is among the most securely reconstructed parts of the proto-lexicon. The number seven held particular significance in many ancient cultures — seven celestial bodies visible to the naked eye, seven days of the week — and the stability of this word may partly reflect its cultural importance.
Notes
Pokorny 909. English seven, September (originally 7th month), heptagon.
Related Roots
English Words from *septm̥
These modern English words descend from this root. Each page traces the full journey from PIE to present-day English.