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.
From O.Fr. intervalle, from L.L. intervallum, originally "space between two palisades or ramparts," from → inter- "between" + vallum "rampart."
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."
Fr.: intervalle genre lumière
The space-time interval between two events if it is zero, i.e. ds2 = 0.
Fr.: intervalle ouvert
An interval that does not include its two endpoints.
Fr.: intervalle espace-temps
Fr.: intervalle genre espace
Fr.: intervalle genre temps