A reference index of astrological terms
Index › E › Elements and modalities
The twelve signs are classified along two axes. The four elements, also called triplicities, group the signs into four sets of three. The three modalities, also called quadruplicities or qualities, group them into three sets of four. Every sign has exactly one element and one modality, and every element-modality pair occurs exactly once, which is the structural reason there are twelve signs and not some other number.
Signs of the same element stand 120 degrees apart and therefore form trines with one another, which is why the element groups are also called triplicities.
Signs sharing a modality stand 90 or 180 degrees apart, so they form squares and oppositions. This is why a square in a chart is normally a same-modality relationship and a trine a same-element one, and why the aspect and the classification are often two descriptions of the same fact.
The element names are inherited from Greek natural philosophy, in which they were held to be constituents of matter. No current practitioner means this literally. The names function as labels for the four groups and any explanatory weight placed on the physical properties of fire or water is added by the writer, not by the system.
The Horoscope Hub is a reference work. Entries describe what practitioners do and what terms mean; they do not endorse astrological claims. Compiled by volunteers — see the contributor list and the editorial method.