syzygy

Either of two points in the orbit of a solar system body where the body is in opposition to or in conjunction with the sun.

Either of two points in the orbit of the moon when the moon lies in a straight line with the sun and Earth.

The configuration of the sun, the moon, and Earth lying in a straight line.

The combining of two feet into a single metrical unit in classical prosody.

In astronomy, the conjunction or opposition of a planet with the sun, or of any two of the heavenly bodies. On the phenomena and circumstances of the syzygies depends a great part of the lunar theory.

In ancient prosody, a group or combination of two feet.

In algebra, a linear function in the variables. See syzygetic.

In zoology, the conjunction of two organs or organisms by close adhesion and partial concrescence, without loss of their identity; also, the thing so formed, or the resulting conformation; a syzygium: a term variously applied.

The point of an orbit, as of the moon or a planet, at which it is in conjunction or opposition; — commonly used in the plural.