In western astrology a Ptolemaic aspect is one of the five major aspects employed in astrological charts. Specifically, the Ptolematic aspects include the conjunction, sextile, square, trine and opposition.
The Ptolemaic aspects are referred to as such because they are the only five aspects that were recognized in the Tetrabiblos of Claudius Ptolemy, which is one of the oldest surviving and most influential texts on horoscopic astrology in the western astrological tradition.
The Ptolemaic aspects are usually contrasted with what are referred to as the non-Ptolemaic aspects, which are any aspects besides those employed by Ptolemy. This would include the aspects introduced by Johannes Kepler in the 17th century, such as the semi-sextile, semi-square, quintile, biquintile and sesquidrate, as well as any aspects introduced by others in later centuries.
As an alternate convention, sometimes the Ptolemaic aspects are referred to as the “major aspects“, while non-Ptolemaic aspects are referred to as “minor aspects”.