octave
noun
oc·tave ˈäk-tiv 
-təv,
-ˌtāv
1
: an 8-day period of observances beginning with a festival day
2
a
: a stanza of eight lines : ottava rima
b
: the first eight lines of an Italian sonnet
3
a
: a musical interval embracing eight diatonic degrees
b
: a tone or note at this interval
c
: the harmonic combination of two tones an octave apart
d
: the whole series of notes, tones, or digitals comprised within this interval and forming the unit of the modern scale
e
: an organ stop giving tones an octave above those corresponding to the keys
4
: the interval between two frequencies (as in an electromagnetic spectrum) having a ratio of 2 to 1
5
: a group of eight
Example Sentences
He sang the song an octave lower.
Recent Examples on the Web The lauded vocalist Kurt Elling uses his four-octave range in surprising ways, dramatically twisting and extending familiar melodies or confidently peppering them with vocalese, never losing an innate sense of swing. 
Stephanie Williams, Washington Post, 25 Aug. 2022 The music, though, has been updated with a small clapping pop beat, accompanied by some high-octave synths and a rhythmic guitar, all leading right up to a drop … until the clip cuts itself off. Stephen Daw, Billboard, 22 Aug. 2022 The regulations specify that AVAS sounds must cover four separate, nonadjacent octave bands. John Seabrook, The New Yorker, 1 Aug. 2022 There are four expressions that comprise this series: 11-year-old single malt from Caol Ila finished in a sherry octave cask, 13-year-old from Ardmore, 14-year-old from Highland Park and 10-year-old from Bunnahabhain. Jonah Flicker, Robb Report, 27 July 2022 Thompson has a low octave voice and his words move at an unhurried pace. Robin Givhan, Washington Post, 28 June 2022 Phillips, an octave-scaling soprano, made her debut at New York’s Metropolitan Opera in 2008. Matt Wake | Mwake@al.com, al, 10 Aug. 2022 Alas, the Dropout star couldn't defy Grande's four-octave range, or really, destiny. Lester Fabian Brathwaite, EW.com, 20 July 2022 Mal could isolate audio, splitting off chatter from guitar strumming, mutters from buzzing amps and, for example, McCartney’s lead vocal as isolated from octave-spanning harmonies by Lennon and Harrison. Fred Schruers, Los Angeles Times, 17 June 2022 See More
Stephanie Williams, Washington Post, 25 Aug. 2022 The music, though, has been updated with a small clapping pop beat, accompanied by some high-octave synths and a rhythmic guitar, all leading right up to a drop … until the clip cuts itself off. Stephen Daw, Billboard, 22 Aug. 2022 The regulations specify that AVAS sounds must cover four separate, nonadjacent octave bands. John Seabrook, The New Yorker, 1 Aug. 2022 There are four expressions that comprise this series: 11-year-old single malt from Caol Ila finished in a sherry octave cask, 13-year-old from Ardmore, 14-year-old from Highland Park and 10-year-old from Bunnahabhain. Jonah Flicker, Robb Report, 27 July 2022 Thompson has a low octave voice and his words move at an unhurried pace. Robin Givhan, Washington Post, 28 June 2022 Phillips, an octave-scaling soprano, made her debut at New York’s Metropolitan Opera in 2008. Matt Wake | Mwake@al.com, al, 10 Aug. 2022 Alas, the Dropout star couldn't defy Grande's four-octave range, or really, destiny. Lester Fabian Brathwaite, EW.com, 20 July 2022 Mal could isolate audio, splitting off chatter from guitar strumming, mutters from buzzing amps and, for example, McCartney’s lead vocal as isolated from octave-spanning harmonies by Lennon and Harrison. Fred Schruers, Los Angeles Times, 17 June 2022 See More Word History
Etymology
Middle English, from Anglo-French, from Medieval Latin octava, from Latin, feminine of octavus eighth, from octo eight — more at eight
First Known Use
14th century, in the meaning defined at sense 1
Kids Definition
octave
noun
oc·tave ˈäk-tiv
1
: a space of eight steps between musical notes
2
: a tone or note that is eight steps above or below another note or tone