In Roman religion, Terminus was the god who protected boundary
markers; his name was the Latin word for such a marker.
Sacrifices were performed to sanctify each boundary stone, and
landowners celebrated a festival called the "Terminalia" in
Terminus' honor each year on February 23. The Temple of
Jupiter Optimus Maximus on the Capitoline Hill was thought to
have been built over a shrine to Terminus, and he was
occasionally identified as an aspect of Jupiter under the name
a Roman divinity presiding over boundaries and frontiers.
His worship is said to have been instituted by Numa who
ordered that every one should mark the boundaries of his
landed property by stones to be consecrated to Jupiter (Ζεὺς
ὅριος), and at which every year sacrifices were to be
offered at the festival of the Terminalia. (Dionys. A. R.
2.9, 74.) These sacred boundaries existed not only in regard
to private property, but also in regard to the state itself,
the boundary of which was not to be trangressed by any
foreign foe. But in later times the latter must have fallen
into oblivion, while the termini of private property
retained their sacred character even in the days of
Dionysius, who states that sacrifices of cakes, meal, and
fruit (for it was unlawful to stain the boundary stones with
blood), still continued to be offered. The god Terminus
himself appears to have been no other than Jupiter himself,
in the capacity of the protector of boundaries. (Ov. Fast.
2.639, &c.; Lactant. 1.20, 37.) The Terminus of the Roman
state originally stood between the fifth and sixth milestone
on the road towards Laurentum, near a place called Festi,
and that ancient/boundary of the ager Romanus continued to
be revered with the same ceremonies as the boundaries of
private estates. (Ov. Fast. l.c. ; Strab. v. p.230.) Another
public Terminus stood in the temple of Jupiter in the
Capitol, and above it there was an opening in the roof,
because no Terminus was allowed to be under cover. (Fest. p.
368, ed. Müller.) This is another proof that Terminus was
only an attribute of Jupiter, although tradition gave a
different reason for this circumstance; for when that temple
was to be founded, and it was necessary to exaugurate other
sanctuaries standing on the same site, all the gods readily
gave way to Jupiter and Juno, but the auguries would not
allow the sanctuaries of Terminus and Juventas to be
removed. This was taken as an omen that the Roman state
would remain ever undiminished and young, and the chapels of
the two divinities were inclosed within the walls of the new
temple. (Serv. ad Aen. 2.575, 9.448; Ov. Fast. 2.671.) Here
we may ask, what had a Terminus to do on the Capitol, unless
he was connected or identical with Jupiter? (Comp. Liv.
1.55, 5.54, 43.13, 45.44; Plb. 3.25 ; Hartung, Die Relig.
der Röm. ii. p. 50, &c.) - A Dictionary of Greek and Roman
biography and mythology, William Smith, Ed.