Larynx. Tax. Syntax. Flax. Wax. Mix. Fix. Ibex. Onyx. Manx. Minx. Jinx. Lynx. Pox. Flex. Reflex. Prefix. Suffix. Affix. Complex. Simplex. Duplex. Triplex. Matrix. Box. Fox. Coccyx.
To list a few more (less than 7 letters):
Ax. Ox. Annex. Apex. Calyx. Flux. Helix. Hex. Icebox. Index. Influx. Latex. Lax. Phlox. Relax. Sex. Suplex. Unisex. Vertex. Vortex. Vex.
To list a few more (7 letters):
Anthrax. Paradox. Phalanx. Pharynx. Perflex.
A more complete list :
14 LettersADMINISTRATRIX
13 LettersULTRAORTHODOX CEPHALOTHORAX ARCHAEOPTERYX
12 LettersPORTMANTEAUX PNEUMOTHORAX HYPERCOMPLEX HETERODUPLEX
11 LettersOVERCOMPLEX NONORTHODOX NEOORTHODOX NASOPHARYNX HYPOPHARYNX HYDROTHORAX
10 LettersUNORTHODOX TROUSSEAUX SUPERHELIX SUBBUREAUX OROPHARYNX NONCOMPLEX METATHORAX MESOTHORAX INHERITRIX GOOGOLPLEX GENERATRIX GASPEREAUX DOMINATRIX COADJUTRIX CIRCUMFLEX CHATTERBOX BORDEREAUX ANTICLIMAX
9 LettersTINDERBOX TESTATRIX SUBCORTEX SUBCLIMAX STRONGBOX SHADOWBOX RETROFLEX RATTLEBOX PROTHORAX PRIEDIEUX PEPPERBOX NEOCORTEX MULTIPLEX METROPLEX MEDIATRIX LETTERBOX HETERODOX FLAMBEAUX FELLATRIX EXECUTRIX DISCLIMAX DIRECTRIX BISECTRIX ANTIHELIX ABOITEAUX ABOIDEAUX
8 LettersVIDEOTEX UNDERTAX TRUMEAUX TRANSFIX TONNEAUX TOADFLAX TABLEAUX SWINEPOX SWEATBOX SUPERTAX SUPERSEX SUPERFIX SUBINDEX SPINIFEX SOUNDBOX SNUFFBOX SMALLPOX SAUCEBOX SARDONYX ROULEAUX RONDEAUX QUINCUNX QUADPLEX PRECIEUX PONTIFEX PLATEAUX PARALLAX ORTHODOX OCTUPLEX MORCEAUX MIREPOIX MILLILUX MICROLUX MEGAPLEX MATCHBOX MANTEAUX LUNCHBOX JAMBEAUX INTERSEX INTERREX INTERMIX HORSEPOX HOMEOBOX HERITRIX HERETRIX HARUSPEX FOURPLEX FABLIAUX EPICALYX ECONOBOX CYBERSEX CURTALAX CRUCIFIX COUTEAUX COTURNIX CICATRIX CHATEAUX CHAPEAUX BREADBOX BORDEAUX BOBBYSOX BICONVEX BATTEAUX BANDEAUX AVIATRIX APPENDIX ANTHELIX AFTERTAX
7 LettersWORKBOX WOODWAX WOODBOX WOADWAX TUBIFEX TRIPLEX TORTRIX TOOLBOX TELEFAX TECTRIX SPANDEX SONOVOX SOAPBOX SIMPLEX SHOEBOX SANDBOX SALTBOX SALPINX RESEAUX REINDEX RECTRIX REANNEX REAFFIX PRINCOX POSTTAX POSTFIX POSTBOX PILLBOX PHOENIX PHARYNX PHALANX PERSPEX PERPLEX PEMPHIX PARADOX PANCHAX PACKWAX OVERTAX OVERMIX OVERLAX OUTJINX ORATRIX NARTHEX MINIMAX MILIEUX MAILBOX LOCKBOX KLEENEX KICKBOX JUKEBOX HUMIDEX HOMOSEX HELLBOX GRAVLAX GEARBOX GATEAUX FUNPLEX FOWLPOX FLUMMOX FIREBOX FEEDBOX FAREBOX EQUINOX EDITRIX COTEAUX CONFLUX COMPLEX COANNEX COALBOX CHAMOIX CELOTEX CASHBOX CARAPAX BUREAUX BROADAX BOOMBOX BEESWAX BATEAUX BANDBOX ARUSPEX APTERYX ANTITAX ANTISEX ANTHRAX ANTEFIX
6 LettersVORTEX VOLVOX VERTEX VERNIX UNISEX THORAX TEABOX SYRINX SYNTAX SURTAX SUFFIX SUBFIX STYRAX STORAX SPHYNX SPHINX SPADIX SMILAX SKYBOX SILVEX SCOLEX REFLUX REFLEX PROLIX PRETAX PREMIX PREFIX POLLEX POLEAX PICKAX PHENIX PEGBOX PAXWAX OUTFOX OUTBOX NONTAX MUSKOX MENINX MATRIX MASTIX LUMMOX LARYNX INFLUX ICEBOX HOTBOX HATBOX HANDAX HALLUX FORNIX EFFLUX EARWAX DUPLEX DIPLEX COWPOX CORTEX CONVEX COMMIX COCCYX CLIMAX CERVIX CAUDEX BOMBYX BOMBAX BOLLOX BOLLIX BIJOUX BIFLEX BANJAX AUSPEX AFFLUX ADIEUX
5 LettersXEROX VARIX UNSEX UNMIX UNFIX UNBOX TELEX SILEX REWAX RETAX REMIX REMEX RELAX REFIX REDUX REDOX RADIX PYREX PHLOX MUREX MIREX LUREX LATEX KYLIX INFIX INDEX IMMIX HYRAX HELIX HAPAX GALAX FEDEX DEWAX DETOX DESEX CYLIX CULEX COMIX CODEX CIMEX CAREX CALYX CALIX BORAX BEMIX BEAUX ANNEX AFFIX ADMIX ADDAX
4 LettersROUX PREX PLEX ORYX ONYX MINX LYNX JINX JEUX ILEX IBEX HOAX FLUX FLEX FLAX FAUX FALX EAUX DOUX CRUX COAX CALX BRUX APEX
3 LettersZAX WAX VOX VEX TUX TAX SOX SIX SEX SAX REX RAX PYX POX PIX PAX NIX MIX MAX LUX LOX LEX LAX KEX HEX GOX FOX FIX FAX DEX COX BOX
2 LettersOX EX AX
