Synchronicity

1. Etymology

Synchronicity is Jung’s coinage for an acausal connecting principle: a meaningful coincidence of inner and outer events without a causal chain that explains the link. Greek syn- (together) + chronos (time)—together-in-time, but the meaning matters more than the clock. Distinct from mere chance coincidence and from causal “influence.”

2. Plain summary

Synchronicity is when something outside lines up with something inside in a way that feels charged with meaning—and you cannot honestly say one caused the other. A dream, idea, or premonition rises; an outer situation matches it. Space and time can feel strangely elastic while the unconscious is in play; when the content is fully conscious, the odd edges often fade.

It is not a license for superstition. Jung treated it as a third option beside causality and chance—especially where psyche and matter seem to touch. It sits near the psychoid border and the collective unconscious, and it can accompany encounters with archetypes or a god-image without proving metaphysics.

Examples (exhaustive house list for this Index lemma — common synchronicity-related figures and motifs named across Jung’s essays and standard Jungian lexica; not a claim that Jung’s CW contains only these):
acausal connecting principle; meaningful but not causal relation; coincidence in time/space with psychological meaning; linking psychic and material (often inorganic) worlds; unconscious image entering consciousness (dream / idea / premonition) + objective situation coinciding; relativity of space and time; synchronistic marginal phenomena vanishing as content crosses into consciousness; evocation by lowering consciousness / trance-adjacent states; astrology–marriage statistical exploration (historical experiment, not proof); third option beside causality and chance (1952 essay tradition); psychoid psyche–matter contact; archetype constellation as frequent accompaniment; projection risk (reading meaning into noise); inflation risk (ego claims cosmic specialness); relation to self / numinous coincidence; clinical caution vs popular “universe sent me a sign” talk.

3. Academic elucidation

In analytical psychology synchronicity names an acausal order of meaningful coincidence proposed to account for phenomena that obey neither straightforward causality nor pure chance. Lexica list multiple definitional angles (acausal principle; meaningful non-causal relatedness; timed coincidence with psychic meaning; psyche–matter link). Descent Press keeps Sharp and Samuels in §4 so lexicon paraphrase never silently becomes Jung’s voice

4. Lexicon

Sharp (1991)

Synchronicity. A phenomenon where an event in the outside world coincides meaningfully with a psychological state of mind. … Synchronicity … consists of two factors: a) An unconscious image comes into consciousness either directly … or indirectly … b) An objective situation coincides with this content. … Jung associated synchronistic experiences with the relativity of space and time and a degree of unconsciousness.

(Sharp, 1991)

Samuels, Shorter & Plaut (1986) 146–147 (List “synchronicity 146–7”):

Synchronicity … defined in several ways: (1) as an ‘acausal connecting principle’; (2) as referring to events meaningfully but not causally related …; (3) as referring to events that coincide in time and space but can also be seen to have meaningful psychological connections; (4) as linking the psychic and the material worlds…

(Samuels, Shorter, & Plaut, 1986, pp. 146–147)

5. CW concordance — sample, not exhaustive

I chose this term because the simultaneous occurrence of two meaningfully but not causally connected events seemed to me an essential criterion. I am therefore using the general concept of synchronicity in the special sense of a coincidence in time of two or more causally unrelated events which have the same or a similar meaning, in contrast to “synchronism”…
(Jung, 1952/1969, CW 8, p. 565, ¶849)

Synchronicity therefore means the simultaneous occurrence of a certain psychic state with one or more external events which appear as meaningful parallels to the momentary subjective state—and, in certain cases, vice versa.
(Jung, 1952/1969, CW 8, pp. 565–566, ¶850)

Synchronicity therefore consists of two factors: a) An unconscious image comes into consciousness either directly … or indirectly … in the form of a dream, idea, or premonition, b) An objective situation coincides with this content.
(Jung, 1952/1969, CW 8, p. 573, ¶858)

… this term has something to do with time or … a kind of simultaneity. Instead of simultaneity we could also use the concept of a meaningful coincidence of two or more events, where something other than the probability of chance is involved.
(Jung, 1951/1969, CW 8, p. 655, ¶969)

See also: synthetic; psychoid; archetype; collective unconscious; god-image; self; projection; inflation; ego; complex; active imagination. transcendent function.

References

Jung, C. G. (1969). On synchronicity. In H. Read, M. Fordham, G. Adler, & W. McGuire (Eds.), The collected works of C. G. Jung (R. F. C. Hull, Trans.) (2nd ed., Vol. 8, p. 655, ¶969). Princeton University Press. (Original work published 1951)

Jung, C. G. (1969). Synchronicity: An acausal connecting principle. In H. Read, M. Fordham, G. Adler, & W. McGuire (Eds.), The collected works of C. G. Jung (R. F. C. Hull, Trans.) (2nd ed., Vol. 8, pp. 565–566, 573, ¶¶849, 850, 858). Princeton University Press. (Original work published 1952)

Samuels, A., Shorter, B., & Plaut, F. (1986). A critical dictionary of Jungian analysis. Routledge.

Sharp, D. (1991). Jung lexicon: A primer of terms & concepts. Inner City Books.