adagio [It]—slow tempo, often implying a lyrical, poignant character
allegretto—moderately quick tempo. slower than allegro but faster than andante
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
divertimento [I], divertissement [F]—amusement, diversion, entertainment, even table music; Typically, a suite of movements (often more than 4) often intended for diversion and pleasure of a lighthearted nature suitable for social occasions. Typically implies a smaller chamber ensemble. The name was common in 18th century for a variety of music, some of which was more serious and profound than its title would suggest. The French divertissement can apply to an entr'acte: dances and airs from other acts.
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