In the theory of Western music, mode (from Latin modus, "measure, standard, manner, way, size, limit of quantity, method") (Powers 2001, Introduction; OED) generally refers to a type of scale. This usage, still the most common in recent years, reflects a tradition dating to the Middle Ages, itself inspired by the theory of ancient Greek music. The word encompasses several additional meanings, however. Authors from the ninth century until the early eighteenth century sometimes employed the Latin modus for interval. In the theory of late-medieval mensural polyphony, modus is a rhythmic relationship between long and short values or a pattern made from them (Powers 2001, Introduction). Since the end of the eighteenth century, the term "mode" has also applied—in ethnomusicological contexts—to pitch structures in non-European musical cultures, sometimes with doubtful compatibility (Powers 2001, §V,1). Regarding the concept of mode as applied to pitch relationships generally, Harold S. Powers describes a continuum between abstract scale and specific tune, with "most of the area between ... being in the domain of mode" (Powers 2001, §I,3).

Eine Kirchentonart (auch Kirchentonleiter, lat. tonus ecclesiasticus) ist eine diatonische, heptatonische, hiatuslose Tonleiter im Halbtonraum.

En musique, un mode d'une gamme est la représentation de cette gamme en fonction de son axe tonal. Un mode comporte les mêmes notes que la gamme dont il est issu mais a une sonorité qui lui est propre, caractérisée par une tonique et par les intervalles entre cette tonique et les autres notes.

In musica, un modo è un insieme ordinato di intervalli musicali che definisce i rapporti gerarchici tra i vari gradi della scala corrispondente. È invalso da tempo l'uso di utilizzare il termine modalità per designare le modalità medievali e rinascimentali, in opposizione al termine tonalità per i modi attuali (in particolare il maggiore e il minore).

Onder modaliteit kan men verstaan: het gebruik van toonladders of modi. (Latijn: modus=wijze van spelen, lees: toonladder). Het woord modi wordt gebruikt als men verwijst naar de kerkmodi, de gebruikelijke toonladders ten tijde van het gregoriaans tot de barokperiode.