The word "conjugate" is used in a variety of ways. For example two vectorsu, and v, are "A-conjugate" if uAv= 0 for matrix A. The most common use without the A is that u and v are conjugate if u is a row vector, v is a column vector with the same dimension, and uv= 0. More generally, u and v may be conjugate if they are pependicular (if their inner product is 0).