Nadi carries eight points in the horoscope match point chart for Gun Milan system in Vedic Astrology. If it shows zero points in match point chart a Dosh is created.
Horoscope denotes Nadi depending upon the placement of Moon in different Constellation(s) or Nakshatra(s) at the time of birth of the individual. Basis these placements three kinds of Nadis are as follows-
Placement of Moon in any of these constellations – Ashwini, Ardra, Punarvasu, Uttara Phalguni, Hasta, Jyeshtha, Moola, Shatabhisha or Poorvabhadrapada in horoscope is known as Aadi Nadi.
Placement of Moon in any of these constellations – Bharani, Mrigashira, Pushya, Poorvaphalguni, Chitra, Anuradha, Poorvashada, Dhanishtha or Uttarabhadrapada in horoscope is known as Madhya Nadi.
Placement of Moon in any of these constellations named Kritika, Rohini, Ashlesha, Magha, Swati, Vishakha, Uttarashada, Shravana or Revati in horoscope is known as Antya Nadi.
In case both Male and Female have different Nadis from each other score is eight is added to horoscope match point chart. If both have same Nadis score is zero and it forms the Nadi Dosh. Nadi Dosh causes divorce or separation if both Male and Female have Aadi Nadi. Nadi Dosh causes death of either one or both if both Male and Female have either Madhya or Antya Nadis. This is the reason people having same Nadi are advised against marriage.
There are some aspects which help reduce the effects of Nadi Dosh
If both persons are born in the same Nakshatra and the Charana or Pada of Nakshatra is different the effect of Nadi Dosh is reduced although both have same Nadi.
If both have same Moon Sign but the birth Nakshatra(s) are different and both have same Nadi the effect of Nadi Dosh is reduced.
If both have same birth Nakshatra and the Moon Signs are different the effect of Nadi Dosh is reduced although both have same Nadi.