Delta, is the name of the fourth letter of the Greek alphabet. In form, Delta uppercase is Δ. A river delta is so named because its shape approximates the upper-case letter delta.
Delta was considered by the ancient Egyptians a symbol of fire and also of God
A triangle. The name of a piece of furniture in a Commandery of Nights Templar, which, being of a triangular form, derives its name from the Greek letter ~. delta. It is also the title given, in the French and Scottish Rites, to the luminous triangle which encloses the Ineffable Name (see Triangle). – Mackey’s Encyclopedia of Freemasonry
The triangle, or Delta, is the mysterious figure of the Eternal. The three letters which you see, signify as follows:—G, at the top of the triangle, “the grand cause of the Masons“: the S, at the left hand, the “submission to the same order”: and the U, at the right hand, the “union that ought to reign among the brethren: which, altogether make but one body, or equal figure in all its parts.” This is the triangle called “equilateral.” The great letter G, placed in the centre of the triangle, signifies “Great Architect of the Universe,” who is God; and in this ineffable name is found all the divine attributes. This letter being placed in the centre of the triangle, is for us to understand that every true Mason must have it profoundly in his heart. – CAPTAIN WILLIAM MORGAN, The Mysteries of Freemasonry pg 171
The Delta, or mystical triangle, is generally surrounded by a circle of rays, called a “glory.” When this glory is distinct from the figure, and surrounds it in the form of a circle (as in the example just given
from Didron), it is then an emblem of God’s eternal glory. When, as is most usual in the masonic
symbol, the rays emanate from the centre of the triangle, and, as it were, enshroud it in their brilliancy,
it is symbolic of the Divine Light. The perverted ideas of the pagans referred these rays of light to their
Sun-god and their Sabian worship. But the true masonic idea of this glory is, that it symbolizes that Eternal Light of Wisdom which surrounds the Supreme Architect as with a sea of glory, and from him, as a common centre, emanates to the universe of his creation, and to which the prophet Ezekiel alludes in his eloquent description of Jehovah: “And I saw as the color of amber, as the appearance of fire round about within it, from the appearance of his loins even upward, and from his loins even downward, I saw, as it were, the appearance of fire, and it had brightness round about.” – Albert G. Mackey, M.D., The Symbolism of Freemasonry
There is no symbol more important in its significance, more various in its application, or more generally diffused throughout the whole system of Freemasonry, than the triangle. An examination of it, therefore, cannot fail to be interesting to the Masonic student.
The equilateral triangle appears to have been adopted by nearly all the nations of antiquity as a symbol of the Deity, in some of his forms or emanations, and hence, probably, the prevailing influence of this symbol was carried into the Jewish system, where the yod within the triangle was made to represent the Tetragrammaton, or sacred name of God. The equilateral triangle, says Brother D. W. Nash (Freemasons Magazine iv, page 294), “viewed in the light of the doctrines of those who gave it currency as a divine symbol, represents the Great First Cause, the Creator and Container of all things, as one and indivisible, manifesting Himself in an infinity of forms and attributes in this visible universe.” Among the Egyptians, the darkness through which the candidate for initiation was made to pass was symbolized by the trowel, an important Masonic implement, which, in their system of hieroglyphics, has the form of a triangle. The equilateral triangle they considered as the most perfect of figures, and a representative of the great principle of animated existence, each of its sides referring to one of the three departments of creation, the animal, vegetable, and mineral. The equilateral triangle is to be found scattered throughout the Masonic system. It forms in the Royal Arch the figure within which the jewels of the officers are suspended. It is in the Ineffable Degrees the sacred Delta, everywhere presenting itself as the symbol of the Grand Architect of the Universe. In Ancient Craft Masonry, it is constantly exhibited as the element of important ceremonies. The seats of the principal officers are arranged in a triangular form, the three Lesser Lights have the same situation, and the Square and Compasses form, by their union on the greater light, two triangles meeting at their bases. In short, the equilateral triangle may be considered as one of the most constant forms of Masonic symbolism.
The right-angled triangle is another form of this figure which is deserving of attention. Among the Egyptians, it was the symbol of universal nature; the base representing Osiris, or the male principle;
the perpendicular, Isis, or the female principle; and
the hypotenuse, Horus, their son, or the product of the male and female principle.
This symbol was received by Pythagoras from the Egyptians during his long sojourn in that country, and with it he also learned the peculiar property it possessed, namely, that the sum of the squares of the two shorter sides is equal to the square of the longest side—symbolically expressed by the formula, that the product of Osiris and Isis is Horus. This figure has been adopted in the Third Degree of Freemasonry, and will be there recognized as the Forty-seventh Problem of Euclid (see Geometry, Circle, Square, and Forty-seventh Problem). – Mackey’s Encyclopedia of Freemasonry
Delta Force is one of the United States’ four secretive tier-one counter-terrorism and Special Mission Units. It’s primary tasks are counter-terrorism, direct action, and national intervention operations, although it is an extremely versatile group capable of conducting many types of covert missions, including, but not limited to, hostage rescues and raids.
Delta Air Lines, is a major airline headquartered in Atlanta, Georgia, in the United States.