h₂yew-

Root meaning to bind or join legally, yielding Latin iūs (law/right) and English justice, jury, judg‌​‌​‌​‌​‌​‍​‍​‌​‌​‌​‌​‌​‍​‌​‍​‌​‍​‌​‍​‍​‌​‍​‍​‍​‍​‌​‌​‌​‍​‍​‌​‌e.

Discussion

The PIE root *h₂yew- (to join, to yoke, to bind together) produced one of the most conceptually far-‌​‌​‌​‌​‌​‍​‍​‌​‌​‌​‌​‌​‍​‌​‍​‌​‍​‌​‍​‍​‌​‍​‍​‍​‍​‌​‌​‌​‍​‍​‌​‌reaching word families in the IE vocabulary, connecting the physical act of yoking oxen to the legal concept of binding by contract and the spiritual discipline of joining body and mind.

Latin iugum (yoke) continues the nominal derivative *yug-óm directly: the physical crossbar that joins two draft animals. English yoke (OE geoc, from PGmc *juką) descends from the same form through the Germanic branch. The word's survival in both Latin and Germanic with the same meaning confirms the PIE speakers' use of yoked draft animals — a crucial piece of evidence for their technological level.

Latin iungere (to join, to yoke) and its compounds generated a vast English vocabulary: join (from OF joindre, from Latin iungere), junction (a joining point), conjunction (a joining together — both grammatical and astronomical), conjugal (pertaining to the marriage yoke — spouses are "yoked together"), conjugate (to inflect a verb through its "yoked" forms), and subjugate (sub-iugāre, "to bring under the yoke" — to conquer and enslave). The word adjust (ad-iustāre, from iustus, which some connect to this root through the concept of "fitting together") may be distantly related.

Sanskrit yugá- (yoke) and the related yoga (literally "yoking, union, discipline" — the practice of joining body, mind, and spirit) provide the Indo-Iranian reflexes. Yoga is etymologically the same word as yoke — a fact that surprises English speakers but that illuminates the root's original semantic range: to yoke is to join, to join is to discipline, to discipline is to unite what is scattered. The Vedic term yugá also meant "age, era" (as in the four yugas of Hindu cosmology), possibly through the concept of a yoked/joined span of time.

Greek zygón (ζυγόν, "yoke") and the derivative zygōtós ("yoked, joined") gave English zygote (the fertilised cell — the "joined" product of sperm and egg) and the combining form zygo- in biological terminology.

The reconstruction of *yug-óm (yoke) alongside *kʷekʷlo- (wheel) and *h₂eḱs-lo- (axle) completes the PIE transport technology package: yoke + wheel + axle = wheeled vehicle drawn by yoked animals. These three words together place PIE firmly in the early Bronze Age.