Tríades

Tríades is the plural form of tríade, a term that, in Portuguese and other Romance languages, denotes a group of three things or persons. The root is tri- meaning three, with the suffix -ade indicating a set or collection. The term is used across disciplines to refer to triads, though its exact sense depends on context.

In chemistry, the historical term extends to Dobereiner's triads, groups of three elements with similar properties and increasing atomic weight. The middle element's atomic weight closely approximates the average of the outer two, as seen in lithium–sodium–potassium and chlorine–bromine–iodine triads. These observations helped in the development of elemental classification, ultimately leading to the periodic table.

In music theory, a tríade (triad) is a three-note chord built by stacking two intervals of a third above the bass note; common forms include major, minor, diminished, and augmented triads. Triads serve as the primary harmonic building blocks in tonal music and can be inverted to place a different chord tone in the bass.

In social science and linguistics, the concept appears as triadic relations and triadic lists, where groups or sequences of three actors or items generate characteristic dynamics or emphasis.

In Portuguese-language analysis, tríade may also refer to rhetorical or stylistic triads, and outside specialized discourse it remains a general label for any trio of related elements.