1. A coal classification based on degree of metamorphism.

2. See <<stack>>

1. The rank of a matrix is its maximum number of linearly independent rows.

2. The rank of a system of homogeneous linear equations equals the rank of the matrix of its coefficients.

3. A tensor in an n-dimensional space is of rank r if it has n^r components.

4. The rank of a group G is the number of elements in the basis of the quotient group of G over the subgroup consisting of all elements of G having finite period.

5. The rank of a place or valuation is equal to the number of proper prime ideals in its valuation ring.

6. The rank of a prime ideal P is the largest number n for which there exists a sequence P₀=P, P₁, P₂, . . . , P_n of prime ideals such that P_i is a subset of P_i-1.

The number of rotational joints belonging to a robot.

The number assigned to an observation if a collection of observations is ordered from smallest to largest and each observation is given the number corresponding to its place in the order.