méh₁n̥s
“moon, month”month
PIE word for moon and month. Gives Latin mēnsis, English "moon", "month", Greek mḗn.
Discussion
The reconstructed noun *méh₁n̥s ("moon, month") derives from the verbal root *meh₁- ("to measure"), treated in Pokorny (IEW 731–732) and Mallory and Adams (EIEC 1997). The moon was conceived by PIE speakers as "the measurer"—the celestial body that measures time through its phases. This transparent etymology reveals a lunar calendar at the heart of PIE timekeeping.
The cognate set is among the most celebrated in comparative linguistics: Sanskrit mā́s- ("moon, month"), Greek mḗn (μήν, "month") and mḗnē (μήνη, "moon"), Latin mēnsis ("month"), Old English mōna ("moon") and mōnaþ ("month"), Old High German māno and mānōd, Old Norse máni and mánaðr, Gothic mēna, Lithuanian mė́nuo, and Old Church Slavonic měsęcь. The English words moon and month both derive from this root, preserving the ancient connection between the lunar body and the temporal unit it defines.
Latin mēnsis ("month") yields the combining form -mester (as in semester, trimester) and menstrual (from mēnstruālis, "monthly"). Greek mḗn gives the combining form meno- in medical vocabulary (menopause, menorrhea).
The underlying root *meh₁- ("to measure") also produces Latin mētīrī ("to measure"), giving English measure, meter, metric, diameter, geometry, and symmetry—all ultimately from the same root as moon. The semantic chain is: to measure → the measurer (moon) → the measured period (month).
In Germanic, the grammatical gender of "moon" varies: masculine in Old English (se mōna) and most Germanic languages, but neuter in some early forms. The word Monday (Old English mōnandæg, "moon's day") preserves the moon's calendrical function. Old Norse Máni was personified as a male deity who drove the moon chariot across the sky.
The laryngeal *h₁ is confirmed by the long vowel in the daughter languages and the absence of colouring.
Notes
From *meh₁- "to measure" — the moon measures time
Related Roots
English Words from *méh₁n̥s
These modern English words descend from this root. Each page traces the full journey from PIE to present-day English.