conjunction

Often denoted with a large "^", used like a \prod (Pi) or an integral sign: x₁ ^ ... ^ x_n is

    n
   /\
  /  \    x
  i = 1    i

Conjunction (conj) is one of the easier rules of inference in propositional logic. It is very simple, but one of the strengths of propositional logic is that it makes even the most simple parts of an argument explicit.

P
Q
Therefore, P*Q (P and Q)

There are cats.
There are dogs.
Therefore: There are cats and dogs.

The reverse of this rule is Simplification.

See also: Modus Ponens, Hypothetical Syllogism, Constructive Dilemma, Addition, DeMorgan's Rule.

Con*junc"tion (?), n. [L. conjunctio: cf. F. conjunction. See Conjoin.]

1.

The act of conjoining, or the state of being conjoined, united, or associated; union; association; league.

He will unite the white rose and the red: Smille heaven upon his fair conjunction. Shak.

Man can effect no great matter by his personal strength but as he acts in society and conjunction with others. South.

2. Astron.

The meeting of two or more stars or planets in the same degree of the zodiac; as, the conjunction of the moon with the sun, or of Jupiter and Saturn. See the Note under Aspect, n., 6.

⇒ Heavenly bodies are said to be in conjunction when they are seen in the same part of the heavens, or have the same longitude or right ascension. The inferior conjunction of an inferior planet is its position when in conjunction on the same side of the sun with the earth; the superior conjunction of a planet is its position when on the side of the sun most distant from the earth.

3. Gram.

A connective or connecting word; an indeclinable word which serves to join together sentences, clauses of a sentence, or words; as, and, but, if.

Though all conjunctions conjoin sentences, yet, with respect to the sense, some are conjunctive and some disjunctive. Harris.

© Webster 1913.