A very close and trusted friend who seems almost a part of yourself.

Roget 17: similarity, resemblance, likeness, similitude, semblance; affinity, approximation, parallelism; agreement etc. 23; analogy, analogicalness^†; correspondence, homoiousia^†, parity.    connaturalness^†, connaturality^†; brotherhood, family likeness.    alliteration, rhyme, pun.    repetition etc. 104; sameness etc. (identity) 13; uniformity etc. 16; isogamy^†.    analogue; the like; match, pendant, fellow companion, pair, mate, twin, double, counterpart, brother, sister; one's second self, alter ego, chip of the old block, par nobile fratrum [Lat.], Arcades ambo^†, birds of a feather, et hoc genus omne [Lat.]; gens de meme famille [Fr.].    parallel; simile; type etc. (metaphor) 521; image etc. (representation) 554; photograph; close resemblance, striking resemblance, speaking resemblance, faithful likeness, faithful resemblance.    ... show more

Roget 711: auxiliary; recruit; assistant; adjuvant, adjutant; ayudante^†, coaid^†; adjunct; help, helper, help mate, helping hand; midwife; colleague, partner, mate, confrere, cooperator; coadjutor, coadjutrix^†; collaborator.    ally; friend etc. 890, confidant, fidus Achates [Lat.], pal, buddy, alter ego.    [criminal law] confederate; accomplice; complice; accessory, accessory after the fact; particeps criminis [Lat.]; socius criminis [Lat.].    aide-de-camp, secretary, clerk, associate, marshal; right-hand, right-hand man, Friday, girl Friday, man Friday, gopher, gofer; candle-holder, bottle-holder; handmaid; servant etc. 746; puppet, cat's-paw, jackal^†.    tool, dupe, stooge, ame damnee [Fr.]; satellite, adherent.    votary; sectarian, secretary; seconder, backer, upholder, abettor, advocate, partisan, champion, patron, friend at court, mediator; angel (theater, entertainment). friend in need, Jack at a pinch, deus ex machina [Lat.], guardian angel, tutelary genius.    ... show more

Roget 759: deputy, substitute, vice, proxy, locum tenens, badli^†, delegate, representative, next friend, surrogate, secondary.    regent, viceregent^†, vizier, minister, vicar; premier etc. (director) 694; chancellor, prefect, provost, warden, lieutenant, archon, consul, proconsul; viceroy etc. (governor) 745; commissioner etc. 758; Tsung-li Yamen, Wai Wu Pu; plenipotentiary, alter ego.    team, eight, eleven; champion.    ... show more

Roget 890: friend, friend of one's bosom; alter ego; best friend, bosom friend, soulmate, fast friend; amicus [Lat.]; usque ad aras [Lat.]; fidus Achates [Lat.]; persona grata.    acquaintance, neighbor, next-door neighbor, casual acquaintance, nodding acquaintance; wellwisher.    favorer, fautor^†, patron, Mecaenas; tutelary saint, good genius, advocate, partisan, sympathizer; ally; friend in need etc. (auxiliary) 711.    comrade, mate, companion, familiar, confrere, comrade, camarade^†, confidante, intimate; old crony, crony; chum; pal; buddy, bosom buddy; playfellow, playmate, childhood friend; bedfellow, bedmate; chamber fellow.    associate, colleague, compeer.    schoolmate, schoolfellow^†; classfellow^†, classman^†, classmate; roommate; fellow-man, stable companion.    best man, maid of honor, matron of honor.    compatriot; fellow countryman, countryman.    shopmate, fellow-worker, shipmate, messmate^†; fellow companion, boon companion, pot companion; copartner, partner, senior partner, junior partner.    Arcades ambo Pylades and Orestes Castor and Arcades ambo Pylades and Orestes Castor and Pollux^†, Nisus and Euryalus [Lat.], Damon and Pythias, par nobile fratrum [Lat.].    host, Amphitryon^†, Boniface; guest, visitor, prot_eg_e.    ... show more

Polish: alter ego