Conjunction may refer to:

In astronomy, a conjunction occurs when two astronomical objects or spacecraft have either the same right ascension or the same ecliptic longitude, usually as observed from Earth. The astronomical symbol for conjunction is ☌ (in Unicode U+260C) and handwritten . The conjunction symbol is not used in modern astronomy. It continues to be used in astrology.

When two objects always appear close to the ecliptic – such as two planets, the Moon and a planet, or the Sun and a planet – this fact implies an apparent close approach between the objects as seen on the sky. A related word, appulse, is the minimum apparent separation on the sky of two astronomical objects.

Conjunctions involve either two objects in the Solar System or one object in the Solar System and a more distant object, such as a star. A conjunction is an apparent phenomenon caused by the observer's perspective: the two objects involved are not actually close to one another in space. Conjunctions between two bright objects close to the ecliptic, such as two bright planets, can be seen with the naked eye.

In grammar, a conjunction (abbreviated CONJ or CNJ) is a part of speech that connects words, sentences, phrases, or clauses. A discourse connective is a conjunction joining sentences. This definition may overlap with that of other parts of speech, so what constitutes a "conjunction" must be defined for each language. In general, a conjunction is an invariable grammatical particle, and it may or may not stand between the items in a conjunction.

The definition may also be extended to idiomatic phrases that behave as a unit with the same function, e.g. "as well as", "provided that".

A simple literary example of a conjunction: "the truth of nature, and the power of giving interest" (Samuel Taylor Coleridge's Biographia Literaria)

Conjunctions may be placed at the beginning of sentences. But some superstition about the practice persists.

Coordinating conjunctions

Coordinating conjunctions, also called coordinators, are conjunctions that join, or coordinate, two or more items (such as words, main clauses, or sentences) of equal syntactic importance. In English, the mnemonic acronym FANBOYS can be used to remember the coordinators for, and, nor, but, or, yet, and so. These are not the only coordinating conjunctions; various others are used, including "and nor" (British), "but nor" (British), "or nor" (British), "neither" ("They don't gamble; neither do they smoke"), "no more" ("They don't gamble; no more do they smoke"), and "only" ("I would go, only I don't have time"). Types of coordinating conjunctions include cumulative conjunctions, adversative conjunctions, alternative conjunctions, and illative conjunctions.