An Etymological Dictionary of Astronomy and Astrophysics

1. Math.: A portion of a real line (i.e. a line with a fixed scale so that every real number corresponds to a unique point on the line)
   between two designated endpoints. → span.
   

2. Music: Difference in pitch between two tones of a scale.

Etymology (EN): From O.Fr. intervalle, from L.L. intervallum, originally “space between two palisades or ramparts,” from → inter- “between”

• vallum “rampart.”

Etymology (PE): Andarvâr, literally “between walls,” from andar-→ inter- + vâr “wall,” as in divâr “wall” (originally “fortress wall,” from *dida-vāra-), variant bâru “wall, rampart, fortification; fort; tower;” Mid.Pers. bâr, var “enclosure, defences, fortress;” Av. var- “castle.”