Here are two indexes to the articles in my “What Is” series, the first arranged in Alphabetical Order and the second in Reverse Chronological order.

The articles are also available in PDF form on GitHub.

## Alphabetical Order

- Fifty “What Is” Articles
- What Is a (Non)normal Matrix?
- What Is a Block Matrix?
- What Is a Blocked Algorithm?
- What Is a Cholesky Factorization?
- What Is a Companion Matrix?
- What Is a Condition Number?
- What Is a Correlation Matrix?
- What is a Diagonally Dominant Matrix?
- What Is a Fractional Matrix Power?
- What Is a Fréchet Derivative?
- What Is a Generalized Inverse?
- What Is a Hadamard Matrix?
- What Is a Householder Matrix?
- What Is a Matrix Function?
- What Is a Matrix Norm?
- What Is a Matrix Square Root?
- What Is a Matrix?
- What Is a Modified Cholesky Factorization?
- What Is a Permutation Matrix?
- What Is a Pseudo-Orthogonal Matrix?
- What Is a QR Factorization?
- What Is a Random Orthogonal Matrix?
- What Is a Rank-Revealing Factorization?
- What Is a Schur Decomposition?
- What is a Sparse Matrix?
- What Is a Symmetric Positive Definite Matrix?
- What Is a Totally Nonnegative Matrix?
- What Is a Tridiagonal Matrix?
- What Is a Unitarily Invariant Norm?
- What Is a Vandermonde Matrix?
- What Is a Vector Norm?
- What Is an LU Factorization?
- What Is an M-Matrix?
- What Is an Orthogonal Matrix?
- What Is A\A?
- What Is Backward Error?
- What Is Bfloat16 Arithmetic?
- What Is Floating-Point Arithmetic?
- What Is IEEE Standard Arithmetic?
- What is Numerical Stability?
- What Is Rounding?
- What Is Stochastic Rounding?
- What Is the Adjugate of a Matrix?
- What is the Cayley–Hamilton Theorem?
- What Is the Complex Step Approximation?
- What Is the CS Decomposition?
- What Is the Determinant of a Matrix?
- What Is the Frank Matrix?
- What Is the Gerstenhaber Problem?
- What Is the Growth Factor for Gaussian Elimination?
- What Is the Hilbert Matrix?
- What Is the Jordan Canonical Form?
- What Is the Kac–Murdock–Szegö Matrix?
- What is the Kronecker Product?
- What Is the Log-Sum-Exp Function?
- What Is the Logarithmic Norm?
- What Is the Matrix Exponential?
- What Is the Matrix Inverse?
- What Is the Matrix Logarithm?
- What Is the Matrix Sign Function?
- What Is the Matrix Unwinding Function?
- What Is the Nearest Positive Semidefinite Matrix?
- What Is the Nearest Symmetric Matrix?
- What Is the Perron–Frobenius Theorem?
- What is the Polar Decomposition?
- What Is the Second Difference Matrix?
- What Is the Sherman–Morrison–Woodbury Formula?
- What Is the Singular Value Decomposition?
- What Is the Softmax Function?
- What Is the Sylvester Equation?
- What Is the Wilson Matrix?
- “What Is” Series

## Reverse Chronological order

- What Is a Schur Decomposition?
- What Is a Permutation Matrix?
- What Is the Matrix Inverse?
- What Is A\A?
- What Is the Jordan Canonical Form?
- What Is the Second Difference Matrix?
- What Is the Frank Matrix?
- What Is the Logarithmic Norm?
- What Is a Tridiagonal Matrix?
- What Is a Blocked Algorithm?
- What Is a Matrix Norm?
- What Is a Vector Norm?
- What Is a Totally Nonnegative Matrix?
- What Is the Perron–Frobenius Theorem?
- What Is the Kac–Murdock–Szegö Matrix?
- What Is the Determinant of a Matrix?
- What Is a Vandermonde Matrix?
- What Is the Wilson Matrix?
- What Is a Rank-Revealing Factorization?
- What Is a Pseudo-Orthogonal Matrix?
- What Is an LU Factorization?
- Fifty “What Is” Articles
- What is a Diagonally Dominant Matrix?
- What Is a Companion Matrix?
- What Is an M-Matrix?
- What Is a Unitarily Invariant Norm?
- What Is the Nearest Positive Semidefinite Matrix?
- What Is the Nearest Symmetric Matrix?
- What Is the Softmax Function?
- What Is the Log-Sum-Exp Function?
- What Is a Modified Cholesky Factorization?
- What Is the Matrix Sign Function?
- What Is a Fractional Matrix Power?
- What Is the Matrix Unwinding Function?
- What Is a (Non)normal Matrix?
- What Is the Matrix Logarithm?
- What Is a QR Factorization?
- What is the Cayley–Hamilton Theorem?
- What Is the CS Decomposition?
- What Is the Singular Value Decomposition?
- What Is the Complex Step Approximation?
- What Is the Sherman–Morrison–Woodbury Formula?
- What Is a Block Matrix?
- What Is a Householder Matrix?
- What is a Sparse Matrix?
- What Is the Sylvester Equation?
- What is the Kronecker Product?
- What Is the Gerstenhaber Problem?
- What Is a Cholesky Factorization?
- What is Numerical Stability?
- What is the Polar Decomposition?
- What Is a Symmetric Positive Definite Matrix?
- What Is the Growth Factor for Gaussian Elimination?
- What Is Stochastic Rounding?
- What Is the Hilbert Matrix?
- What Is a Fréchet Derivative?
- What Is the Adjugate of a Matrix?
- What Is a Matrix Function?
- What Is Bfloat16 Arithmetic?
- What Is the Matrix Exponential?
- What Is a Matrix Square Root?
- What Is IEEE Standard Arithmetic?
- What Is Floating-Point Arithmetic?
- What Is Rounding?
- What Is a Random Orthogonal Matrix?
- What Is a Correlation Matrix?
- What Is a Hadamard Matrix?
- What Is an Orthogonal Matrix?
- What Is a Generalized Inverse?
- What Is a Matrix?
- What Is Backward Error?
- What Is a Condition Number?
- “What Is” Series