A point in space, not a body
Black Moon Lilith is not a planet, a moon or an asteroid. It is a calculated point: the lunar apogee, the spot in the Moon's oval orbit where it is farthest from Earth, projected onto the zodiac.
The name sometimes confuses people, because there is also an asteroid called Lilith. They are different things. Astrologers who speak of Black Moon Lilith mean the apogee point, and that is what this calculator shows.
Why we show mean Lilith
The Moon's orbit is constantly nudged by the Sun, so the true apogee jumps around quite a lot, sometimes by many degrees within weeks. Mean Lilith averages that motion into a smooth, steady path.
Many astrologers who work with Lilith use the mean position, and it is the one we calculate. The true and so-called corrected versions exist too, and they can land in a different sign, so if you see another value elsewhere, the method may be the reason.
Nine months per sign
Mean Lilith moves forward through the zodiac and completes a full circle in about 8.85 years. That works out to roughly nine months in each sign.
So your Lilith sign is shared by everyone born within a span of several months. The house it sits in, along with any close aspects it makes to your planets, gives it a more individual flavor. Both need your birth time.
The themes linked with Lilith
In modern astrology, Black Moon Lilith is associated with the parts of a person that resist being tamed: independence, raw honesty, desire and the feelings someone may have learned to hide. It is often described as the untamed or rejected side of the self.
Readers look at Lilith's sign to describe the style of that independent streak, and at its house for the area of life where it is said to show up. These are symbolic readings, used for reflection rather than to forecast events.
How Lilith fits with the rest of the chart
Because Lilith comes from the Moon's orbit, many astrologers compare it with the natal Moon. Find yours on the moon sign calculator.
The lunar nodes are another set of points drawn from the same orbit, available on the North Node calculator. Your birth chart places Lilith on the wheel with every planet.