Bah. I saw the title of this thread and thought "Oh! I needed to know that recently."
For those who are interested, a matrix is invertible if its determinant is invertible. (In the real numbers, the only non-invertible determinant is 0, but you can be working in a modulus system, where not every number has a multiplicative inverse)
Actually I am also quite fond of math, seeing it is what I need to use for most of my time while trying to learn how to care for reptiles and plants at the same time so that I can become a professional. Also I use it a lot in my drawings to measuring how big, small, thin or wide I need to make it the object and how to get the right or preferable perspective of that object.
I can't explain why math is so interesting to me, but I use it almost every day to make sense of algorithms in computer science. For instance, linear algebra is very useful in coding theory and cryptology.
I find math to be quite bewildering seeing that everytime we discover something about math, it just opens an uncountable array of undiscovered knowledge, and so my interest in it will never die.
