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
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
espressivo [It], con espressione, expressif [Fr]—expressive, with expression.with feeling
opus [L], opera[pl], Op., Opp, WoO, Op. posth—work, as in a work of art. For unique identification, publishers/composers often assign an "opus number", abbreviated as "Op." (e.g. Op. 1). A range of works by opus number, uses the plural "opp." (e.g. "Opp. 1-3"). A single opus number may refer to a collection of works (e.g. a set of quartets) giving rise to designations like "Op. 1, No. 4". For misc. works without opus numbers, "WoO" is often used (e.g."Without Opus"). Posthumously assigned numbers may use "Op. posth". Opus numbers may not precisely reflect chronology (publication vs. composition), can be erroneous, sparse or duplicative. Thus, the works of some historically important composers may use separate catalog numbers (e.g. Bach, Haydn, Schubert). See wiki
sonata [I], sonate [pl], suonato—Originally, "sounded" rather than "sung" (sonar vs. cantar), i.e. 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" and applies to instrumental sonatas, string quartets, symphonies, etc., all examples of the sonata principle. In general usage as a specific work title (e.g. violin sonata), it designates a multi-movement piece for solo or duo instruments with one of the instruments enjoying a feature role. wiki
troppo [I], non troppo, trop [F]—too, too much. non troppo means "not too much". e.g. "Allegro ma non troppo" means fast, but not too much