x1=k1 (mass/si'o) is an equivalence class within/is a substructure of
x2 (mathematical structure/object/category/set endowed with operations and properties) with defining characteristic/property/for similarity/under equivalence relation x3=p3, with representative member x4=p1=p2, in geometry/by standard/under paradigm x5=p4
x1=j2=p3 (ka; jo'u/fa'u term) is the minor difference in/between x2=p2 and x3=p1 that is to be ignored, their similarity being by standard/in geometry x4; x2 is the same as/similar to/parallels x3 in standard/geometry x4 up to/modulo/except for/ignoring unimportant difference x1;
x1 is an atomic element in group x2 [usually, vertical column; denotes electron configuration and, thereby, chemical similarity with vertical neighbors] and period x3 [usually, horizontal row; denotes similarity in size with horizontal neighbors, as well as having the same number and type of electron shells as them] and belonging to other 'class'/'category'/'type'/having other properties x4
according to scheme/organization pattern/standard/periodic table x5.
x1 is an eigenvalue (or zero) of linear transformation/square matrix x2, associated with/'owning' all vectors in generalized eigenspace x3 (implies neither nondegeneracy nor degeneracy; default includes the zero vector) with 'eigenspace-generalization' power/exponent x4 (typically and probably by cultural default will be 1), with algebraic multiplicity (of eigenvalue) x5
x1 is a clade/cladus/monophyletic class formed by most-recent common ancestor(s) x2 and all lineal descendants thereof in family/directed tree structure/according to relationship or standard x3.
x1 is a strict/proper sub-x2 [structure] in/of x3; x2 is a structure and x1 and x3 are both examples of that structure x2 such that x1 is entirely contained within x3 (where containment is defined according to the standard/characteristics/definition of x2; but in any case, no member/part/element that belongs to x1 does not also belong to x3), but there is some member/part/element of x3 that does not belong to x1 in the same way.
x1 is an atomic element in group x2 [usually, vertical column; denotes electron configuration and, thereby, chemical similarity with vertical neighbors] and period x3 [usually, horizontal row; denotes similarity in size with horizontal neighbors, as well as having the same number and type of electron shells as them] and belonging to other 'class'/'category'/'type'/having other properties x4
according to scheme/organization pattern/standard/periodic table x5.