Symbol

1. Etymology

Symbol (Greek symbolon, a token of recognition—two halves that fit) is, for Jung, the best possible expression for something relatively unknown. It is not a mere label. Distinct from a sign (which points to something known). Related: symbolic vs semiotic interpretation; the living symbol in the transcendent function.

2. Plain summary

A symbol says more than we can yet say in plain words. It is the best available picture of a fact we sense but cannot finish defining. A badge on a uniform is a sign—it tells you a known rank. A cross can be treated as a sign (“means divine love”) or as a symbol (points beyond every finished explanation to something still unknown).

Jung broke with a view that treats dream images only as symptoms of already-known wishes. True symbols are intuitive formulations that cannot yet be said better another way. They appear in dreams, visions, and fantasy; they carry the transcendent function when opposites need a third; they can be emptied into signs by over-explanation or inflated by ego claims (inflation).

Examples (exhaustive house list for this Index lemma — common symbol-related figures and motifs named across Jung’s essays and standard Jungian lexica; not a claim that Jung’s CW contains only these):
best possible expression of something unknown; psychological expression stating more than itself; symbol vs sign (insignia = signs); semiotic vs symbolic interpretation of unconscious material; cross as semiotic vs symbolic cases; Freud critique (signs/symptoms vs true symbols); intuitive idea not yet formulable another/better way; relatively unknown fact postulated as existing; living vs dead symbol; symbol in dreams / visions / active imagination; vehicle of transcendent function; archetype appearing as symbolic image (not the archetype as such); god-image as numinous symbol of totality; self mandala / quaternity imagery; shadow / anima/animus personifications as symbolic figures; complex personification; projection of symbolic content onto outer carriers; risk of reducing symbol to allegory; constructive / final interpretation (adjacent Sharp heads).

3. Academic elucidation

In analytical psychology a symbol is defined by its relation to the unknown: the chosen expression is the best available formulation of a relatively unknown fact. Lexica mark the break with a purely semiotic (sign/symptom) reading of unconscious contents and locate the symbol as the mediating form in the transcendent function. Descent Press keeps Sharp and Samuels in §4 so lexicon paraphrase never silently becomes Jung’s voice

4. Lexicon

Sharp (1991)

Symbol. The best possible expression for something unknown. … Every psychological expression is a symbol if we assume that it states or signifies something more and other than itself which eludes our present knowledge. … Jung distinguished between a symbol and a sign. … the images can be interpreted semiotically, as symptomatic signs pointing to known or knowable facts, or symbolically, as expressing something essentially unknown.

(Sharp, 1991)

Samuels, Shorter & Plaut (1986) 144–146 (List “symbol 144–6”):

Symbol … Jung’s theoretical break with Freud was partly over the issue of what is to be meant by ‘symbol’… ‘Those conscious contents which give us a clue to the unconscious background are incorrectly called symbols by Freud. They are not true symbols… merely the role of signs or symptoms… The true symbol differs essentially… an intuitive idea that cannot yet be formulated in any other or better way.’ … ‘A symbol always presupposes that the chosen expression is the best possible description or formulation of a relatively unknown fact…’

(Samuels, Shorter, & Plaut, 1986, pp. 144–146)

5. CW concordance — sample, not exhaustive

A symbol always presupposes that the chosen expression is the best possible description or formulation of a relatively unknown fact, which is none the less known to exist or is postulated as existing.
(Jung, 1921/1971, CW 6, p. 653, ¶814)

Every view which interprets the symbolic expression as an analogue or an abbreviated designation for a known thing is semiotic. A view which interprets the symbolic expression as the best possible formulation of a relatively unknown thing … is symbolic. A view which interprets the symbolic expression as an intentional paraphrase or transmogrification of a known thing is allegoric.
(Jung, 1921/1971, CW 6, p. 653, ¶815)

So long as a symbol is a living thing, it is an expression for something that cannot be characterized in any other or better way. The symbol is alive only so long as it is pregnant with meaning.
(Jung, 1921/1971, CW 6, p. 654, ¶816)

Those conscious contents which give us a clue to the unconscious background are incorrectly called symbols by Freud. They are not true symbols, however, since according to his theory they have merely the role of signs or symptoms of the subliminal processes. The true symbol differs essentially from this, and should be understood as an expression of an intuitive idea that cannot yet be formulated in any other or better way.
(Jung, 1922/1966, CW 15, p. 70, ¶105) 69).

See also: synthetic; transcendent function; active imagination; archetype; psychoid; god-image; self; individuation; complex; projection; inflation; shadow; anima; animus; collective unconscious. compensation.

References

Jung, C. G. (1966). On the relation of analytical psychology to poetry. In H. Read, M. Fordham, G. Adler, & W. McGuire (Eds.), The collected works of C. G. Jung (R. F. C. Hull, Trans.) (Vol. 15, p. 70, ¶105). Princeton University Press. (Original work published 1922)

Jung, C. G. (1971). Definitions: Symbol. In H. Read, M. Fordham, G. Adler, & W. McGuire (Eds.), The collected works of C. G. Jung (R. F. C. Hull, Trans.) (Vol. 6, pp. 653–654, ¶¶814, 815, 816). Princeton University Press. (Original work published 1921)

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.