The-three-unities

plural noun
1.
See under unity (def 8).
noun, plural unities.
1.
the state of being one; oneness.
2.
a whole or totality as combining all its parts into one.
3.
the state or fact of being united or combined into one, as of the parts of a whole; unification.
4.
absence of diversity; unvaried or uniform character.
5.
oneness of mind, feeling, etc., as among a number of persons; concord, harmony, or agreement.
6.
Mathematics.

the number one; a quantity regarded as one.
identity (def 9).

7.
(in literature and art) a relation of all the parts or elements of a work constituting a harmonious whole and producing a single general effect.
8.
one of the three principles of dramatic structure (the three unities) derived from Aristotelian aesthetics and formalized in the neoclassic canon in which a play is required to represent action as taking place in one day (unity of time) as occurring within one place (unity of place) and as having a single plot with a beginning, middle, and end (unity of action)
noun (pl) -ties
1.
the state or quality of being one; oneness
2.
the act, state, or quality of forming a whole from separate parts
3.
something whole or complete that is composed of separate parts
4.
mutual agreement; harmony or concord: the participants were no longer in unity
5.
uniformity or constancy: unity of purpose
6.
(maths)

the number or numeral one
a quantity assuming the value of one: the area of the triangle was regarded as unity
the element of a set producing no change in a number following multiplication

7.
the arrangement of the elements in a work of art in accordance with a single overall design or purpose
8.
any one of the three principles of dramatic structure deriving from Aristotle’s Poetics by which the action of a play should be limited to a single plot (unity of action), a single location (unity of place), and the events of a single day (unity of time)