I'm a neuroscientist, but I don't know much maths. I like to learn the functions, and what they mean exactly and how/when I should use them. I'm specifically interested in knowing what mathematical functions actually mean and what I'm supposed to understand from them.
I want to read a little bit of maths every day and gradually build my knowledge over a year or two, and continue like that for a few years. What book do you recommend me to read (or start with)?
Edit: As some users correctly pointed out I should set the spectrum. The things that we use most are: Algebra, integrals and derivatives, logarithms, and trigonometric functions.
There is even a Journal of Mathematical Neuroscience. An important part in neuroscience seems to be discrete mathematics. So I recommend books in discrete mathematics, e.g., see this question. Of course, like learning any other language, one should follow a grammar, and learn the vocabulary. Here I recommend the usual classes in analysis, linear algebra and abstract algebra.