allegro [I]—fast, lively tempo. From the Italian word for cheerful or gay.
andante [I]—moderately slow tempo (e.g. walking). Faster than adagio but slower than allegretto
brio [I], con brio, brioso—vigor, vigorously, with fire
chamber music, Kammermusik [G], musique de chambre [F], musica da camera [I], musica cameralis [L]—"Classical Music" for a small ensemble, generally 8 or fewer players with a canonical emphasis on 3-6 players. explore
duo, duet, dueto [S], duetto [I], duett [G]—a work for two instruments; the ensemble itself
fantasia, fantasy, fantazy, fantazia, phantasy, phantasie, fancy, fantasie [G], fantaisie [F] —generally, a piece of music favoring a free flight of expression over strict adherence to formal rules; suggesting an improvisational character. However, there are at least two more specific historical meanings: 1) the fantasia/fantasie/fancy of English Renaissance viol consort music and 2) Cobbett's Phantasie, an early 20th century form of single-movement chamber music inspired by the Renaissance fancy with the goal of stimulating new English chamber or "consort" music.
moderato [I], moderamente, modéré [F], modérément [F]—moderately, at a moderate tempo, applying a touch of restraint to its related word(s), e.g. allegro moderato
rondo—sectional movement form featuring a recurring refrain between contrasting episodes in a variety of plans, a typical one being ABACABA (A is the refrain; B and C are episodes). Often used for finales.
rubato—to artfully distort the rhythmic flow for expressive emphasis by slowing (speeding) the tempo around certain points of articulation. Meaning "robbed" time suggesting that a slowing must be balanced by a speeding up
sonata, sonate, suonato—a complicated term. Originally, "sounded" rather than "sung" (sonar vs. cantar), e.g. instrumental music. According to historical period, sonata began to imply a formal plan of movements as well as the structure within a single movement, e.g. sonata form. In general usage as a work title, it designates a multi-movement piece for solo or duo instruments with one of the instruments enjoying a feature role.
sostenuto [I], soutenu [F]—sustained, perhaps a bit slow
violin sonata—a multi-movement work for violin and keyboard (or continuo) though there are sonatas for solo violin as well as sonatas in a single movement. While the violin would seem to be the featured instrument, many sonatas starting with the classical period find the piano to be an equal partner in the sense of a chamber work for two players.