A neji (pronounced /nɛdʒi/ "nedgy"; for "near-equal JI") is a circulating temperament which approximates an equal tuning dividing a JI equave with a subset of a mode of the harmonic series. It is often informally used for a harmonic series approximation of any non-JI scale, e.g. "neji Lydian".
In Zhea Erose's primodality theory, nejis can be used to explore a prime family (see primodality), while keeping the transposability, scale structures, rank-2 harmonic theory, notation, etc. associated with that edo. (The neji's denominator need not be prime but primes may be preferred for sake of minimizing lower-complexity intervals. Zhea often uses semiprimes pq.) Zhea Erose's theory also deals with modulations between different prime families, and combining different prime families into one scale.
Nejis are distinct from detempering. Unlike detempering, a neji need not imply a mapping. Meanwhile, detempering in general does not require the rational pitch replacements to all be part of the same harmonic series. Nejis are compatible with regular temperament theory if they are treated as working in the concrete tuning layer of temperaments.