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HYPHEN
WORDNET DICTIONARY
OXFORD DICTIONARY
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WORDNET DICTIONARY

Noun duo has 4 senses

• duo(n = noun.quantity) brace, couple, couplet, distich, duad, duet, dyad, pair, span, twain, twosome, yoke - two items of the same kind; Array
has parts: fellow, mate
is a kind of 2, deuce, ii, two
has particulars: doubleton

• duo(n = noun.group) duet, duette - two performers or singers who perform together; Array
has particulars: laurel and hardy
is a kind of musical group, musical organisation, musical organization

• duo(n = noun.group) couple, duet, twosome - a pair who associate with one another; "the engaged couple"; "an inseparable twosome"
is a kind of pair
has particulars: same-sex marriage

• duo(n = noun.communication) duet, duette - a musical composition for two performers; Array
has parts: primo, secondo
is a kind of composition, musical composition, opus, piece, piece of music

OXFORD DICTIONARY

THESAURUS

duo

both, brace, couple, couplet, distich, double harness, doublet, duad, duet, duettino, dyad, ensemble music, ensemble singing, match, mates, octet, pair, part music, part singing, part song, polyphonic music, quartet, quintet, septet, septuor, sestet, set of two, sextet, span, team, terzet, terzetto, the two, trio, twain, two, twosome, yoke

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duo

Music

N music, concert, strain, tune, air, melody, aria, arietta, piece of music, work, number, opus, sonata, rondo, rondeau, pastorale, cavatina, roulade, fantasia, concerto, overture, symphony, variations, cadenza, cadence, fugue, canon, quodlibet, serenade, notturno, dithyramb, opera, operetta, oratorio, composition, movement, stave, passamezzo, toccata, Vorspiel, instrumental music, full score, minstrelsy, tweedledum and tweedledee, band, orchestra, concerted piece, potpourri, capriccio, vocal music, vocalism, chaunt, chant, psalm, psalmody, hymn, song, canticle, canzonet, cantata, bravura, lay, ballad, ditty, carol, pastoral, recitative, recitativo, solfeggio, Lydian measures, slow music, slow movement, adagio, minuet, siren strains, soft music, lullaby, dump, dirge, pibroch, martial music, march, dance music, waltz, solo, duet, duo, trio, quartet, quartett, septett, part song, descant, glee, madrigal, catch, round, chorus, chorale, antiphon, antiphony, accompaniment, second, bass, score, bourdon, drone, morceau, terzetto, composer, musician, musical, instrumental, vocal, choral, lyric, operatic, harmonious, Wagnerian, adagio, largo, larghetto, andante, andantino, alla capella, maestoso, moderato, allegro, allegretto, spiritoso, vivace, veloce, presto, prestissimo, con brio, capriccioso, scherzo, scherzando, legato, staccato, crescendo, diminuendo, rallentando, affettuoso, obbligato, pizzicato, desto, in notes by distance made more sweet, like the faint exquisite music of a dream, music arose with its voluptuous swell, music is the universal language of mankind, music's golden tongue, the speech of angels, will sing the savageness out of a bear, music hath charms to soothe the savage beast.

For further exploring for "duo" in Webster Dictionary Online