solfège
A music education system that assigns syllables (do, re, mi, fa, sol, la, ti) to the notes of a scale for sight-singing and ear training.
In Depth
Solfège (from the Italian solfa) uses a set of syllables to represent musical pitches, enabling singers to sight-read and internalize interval relationships. In "fixed do" solfège (standard in France and Italy), do always equals C regardless of key. In "movable do" solfège (common in English-speaking countries and Hungary), do shifts to represent the tonic of whatever key the music is in, making it a tool for understanding tonal relationships rather than absolute pitch.
The system dates back to the 11th-century monk Guido d'Arezzo, who derived the syllables from the first syllables of each line of a Latin hymn to St. John the Baptist: Ut queant laxis, Resonare fibris, Mira gestorum, Famuli tuorum, Solve polluti, Labii reatum. "Ut" was later replaced by "do" (from Dominus) in most traditions, and "ti" (or "si") was added for the seventh degree. Solfège remains the foundation of music education worldwide, from elementary classrooms to conservatory ear-training courses.
The syllables do-re-mi became so universally known that Rodgers and Hammerstein built an entire song around them in The Sound of Music — making an 11th-century monk's teaching tool into a 20th-century pop hit.