An expert is someone who knows everything about a subject and can look at it from beyond the borders of its context. Knowing everything can be read as: made eve

An expert is someone who knows everything about a subject and can look at it from beyond the borders of its context. Knowing everything can be read as: made every possible mistake, or perhaps: re-created the entire concept. Or maybe even: did an exhaustive search of all the possible avenues of thinking/applying/using the subject at hand. It also depends on who you ask. Some people have a different mental model of the meaning of words or the values attached to them. It can be as simple as: "the person that I ask stuff from and always has the answer" or as complex as "this person doesn't just read, repeat or know the theory or know the abstract theory but is even beyond that". How do _you_ become an expert? It depends. What do you think an expert should be? Find that, then find where you are and the gap between that and where you need to be and start working on it. An expert at walking your own dog has a different route than say, an expert at silicon substrate doping. Since we are on Hacker News, we could take being an expert at Linux Device Drivers as a subject. You'd be able to read and test and expand as much as you'd like until you become the expert you desire to be. Examples, documents and sources are all available. It does require base knowledge to build on; i.e. building software, writing and reading C, the specifics of the kernel, the specifics of the kernel build system. At some point if you know how to create and build a module that is a driver, you'd be a beginner and you can start becoming advanced by perhaps expanding on your knowledge by nibbling at the borders of the subject; the build system itself, the configuration system, the hardware underpinnings for drivers. Next you might become interested in memory maps and CPU architectures. At some point you can understand end-to-end how a click of a button translates into an event. You'd be advanced. Now take all of those concepts and things you're reading and the parts you've designed. That is a single subjects within borders. When you go beyond that, i.e. design the theories that define it you're an expert. Not only can you build and work with it, understand its context and modify it at will, but you can re-define and create it based on your own expert knowledge and abstract theory behind the concepts and implementations. You can also make it much smaller than that. I.e. become an expert at folding t-shirts. Still means you need to know about folding, fabrics, speed vs. quality, quantity vs. quality (are you folding t-shirts for yourself or for a warehouse? is it manual or automated?). Once you know how to define what folding means and how it is affected and how it affects its context (i.e. what happens to the fibers? and what if it's dirty, or new? or when it has been washed 10 times? what about 100?) you could pretty much call yourself a t-shirt folding expert. This is still big, but a lot smaller than a software example.