Eni (ἔνι) is a contracted form of enesti — it is present within, there is among. It appears in Paul's great equality passages (Galatians 3:28; Colossians 3:11) to say "there is no" (Greek, Jewish/Greek, slave/free, male/female) — categories that have ceased to mark division in Christ.
Paul's use of eni ("there is no...") in Galatians 3:28 is one of the NT's most radical social statements. The categories he negates — Jew/Greek, slave/free, male/female — were the great stratifying distinctions of ancient society. In Christ, eni (there is) no such division. This is not the erasure of identity but the erasure of hierarchy: all are "one in Christ Jesus." The eni construction — "there is no" — functions as a present-tense declaration: in the community of Christ, these distinctions no longer carry their old segregating power.
Eni is the contracted, emphatic form — its shortness is its power. Where the longer form (enesti) would be expected, the abbreviated eni punches harder. The negative ouk eni = "it does not exist within" — not "it is less prominent" but "it has no existence" as a dividing force. This is eschatological present tense: the new creation's reality claimed in the present community.