As nouns the difference between menstruant and niddah
is that menstruant is a woman who is menstruating while niddah is someone whom halacha considers menstruant.
As an adjective menstruant
is menstruating.
menstruant
English
Noun
(
en noun)
A woman who is menstruating.
Adjective
(-)
Menstruating.
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niddah
English
Noun
(
en noun)
(Judaism) Someone whom halacha considers menstruant.