Applying and separating refer to whether two planets are moving toward an exact aspect (applying) or away from being exact (separating).

An aspect is the geometric relationship between planets and/or points, based on them being a certain number of degrees apart.

When a planet or the Moon is conjunct the Sun within 17 minutes of arc (some say within 1 degree), it is said to be Cazimi. This condition makes the planetary energy very strong.

When two planets are not in orb to share an aspect, but a third planet is in orb with both, it can bridge the gap that activates the aspect between the other two planets.

When a planet is conjunct the Sun within 8½ degrees, it is said to be Combust. Its energy is considered to be weakened.

The Conjunction is a geometric aspect between two planets that are at roughly the same degree. It indicates a merging of their energies to form a new dynamic.

When two planets are contra-parallel, they are the same distance from the Earth's equator in Declination, but one is north and the other is south. Contra-parallel planets needn't have any aspect between them, although are often viewed as if they were in opposition.

A Dissociate Aspect is a major aspect between planets that are in signs that do not share an element, modality or polarity, yet they are within a reasonable orb to still be in aspect to each other. Also called an out-of-sign aspect.

Inconjunct is often used as a synonym for the quincunx aspect (150°), and sometimes also refers to a semi-sextile aspect (30°).

The Opposition is an aspect between two planets that are 180 degrees apart (give or take a few degrees of orb). Its energy is typically stressful and polarizing, but can also bring a complementary balance.

Two planets are in aspect when they are a certain number of degrees apart, give or take a certain number of degrees. Those "give-or-take degrees" is the aspect orb.

Planets are parallel when they are have the same Declination, and both are on the same side of the equator, north or south.

Ptolomaic aspects are the conjunction (0°), sextile (60°), square (90°), trine (120°) and opposition (180°). Their name comes from Claudius Ptolemy who advocated using these aspects in chart analysis.

The Quincunx is a geometric aspect between two planets that are approximately 150° apart. It indicates an irritating relationship between the planetary energies.

The Semi-Sextile is a geometric aspect between two planets that are approximately 30° apart. It indicates either an annoying or mildly pleasant relationship between the planetary energies.

When two planets are 45° degrees apart (give or take a few degrees of orb) they are in a Semisquare aspect (sometimes called an Octile). Its effect is irritating and annoying but can also be motivating.

When two planets are 135° degrees apart (give or take a few degrees of orb) they are in a Sesquiquadrate aspect (sometimes called a Tri-Octile). Its effect is irritating, annoying and sometimes triggers anxiety, but can also be motivating.

The Sextile is an aspect between two planets that are 60 degrees apart (give or take a few degrees of orb). The aspect is typically creative, easy-flowing and often indicates natural ability.

The Square Aspect joins planets that are 90 degrees apart (give or take a few degrees of orb). This aspect typically indicates stress and conflict, but can also be motivating and dynamic.

The Trine is a geometric aspect between two planets that are approximately 120° apart. It indicates an easy-flowing relationship between the planetary energies.

Waxing refers to when two planets are moving farther apart (after conjunction and before opposition). Waning is when two planets are moving closer together (after opposition and before conjunction). They tend to indicate a building or dissipation of energy.