Synastry is a method of comparing two individual birth charts to determine the compatibility between them. It involves overlaying the two charts and analyzing the aspects between the planets in each chart.

An aspect is the angular relationship between two planets in a birth chart. The most common aspects are the conjunction, opposition, square, trine, and sextile.

Parallel is not a type of aspect in astrology. The four main types of aspects are the conjunction, opposition, square, and trine.

A sign is a section of the zodiac. There are 12 signs in the zodiac, each of which is associated with a particular set of personality traits and characteristics.

Libra is not a sign of the zodiac. The 12 signs of the zodiac are Aries, Taurus, Gemini, Cancer, Leo, Virgo, Libra, Scorpio, Sagittarius, Capricorn, Aquarius, and Pisces.

A house is a division of the birth chart. There are 12 houses in a birth chart, each of which represents a different area of life.

The Vertex is not a house in the birth chart. The four main houses in the birth chart are the Ascendant, the Midheaven, the Descendant, and the Nadir.

A planet is a celestial body that orbits the Sun. The planets in astrology are Mercury, Venus, Mars, Jupiter, Saturn, Uranus, Neptune, and Pluto.

Pluto is no longer considered a planet in astrology. The eight planets in astrology are Mercury, Venus, Mars, Jupiter, Saturn, Uranus, Neptune, and Pluto.

Retrograde is a term used to describe when a planet appears to be moving backwards in its orbit. This is an optical illusion caused by the relative positions of the Earth and the planet in question.

Saturn is not a retrograde planet. The planets that can be retrograde are Mercury, Venus, Mars, Jupiter, and Uranus.

Dignity is a term used to describe when a planet is in a sign that it rules or is exalted in. A planet is in its dignity when it is in a sign that it is most comfortable in.

Triplicity is not a dignity for a planet. The four dignities for a planet are rulership, exaltation, term, and face.

Debility is a term used to describe when a planet is in a sign that it is weakest in. A planet is in its debility when it is in a sign that it is most uncomfortable in.

Peregrine is not a debility for a planet. The three debilities for a planet are detriment, fall, and anareta.