For i, j, k, l, m, n is an element of {1, 2, 3, 4}, the notion of (T ( i, j), I (k, l), F (m, n)) - interval neutrosophic subalgebra in BCK/BCI-algebra is introduced, and their properties and relations are investigated. The notion of interval neutrosophic length of an interval neutrosophic set is also introduced, and related properties are investigated.