One of the topics I see most often on the forum is a noob asking the question Was I Lucid? The answer seems to be yes 99% of the time, and seeing these posts gets extremely annoying. Lucid dreaming is defined as knowing that you are dreaming. There is no mention in the definition of dream control, or stability. Therefore, the second you realize you are dreaming, you are lucid! It doesn't matter if you wake up a second later, or have no control, it was still a Lucid Dream just because you said something like, "I am dreaming," or, "I am lucid". There is now such thing as 10% Lucidity, or 75% Lucidity, or half Lucidity, or whatever. You knew you were dreaming, so you were lucid!

The reason people ask this is that they confuse being lucid, with how "good" a Lucid you are having. In truth it really boils down to two levels; non-Lucidity and Lucidity, and the rest of it is not how Lucid you are, but how much control, stability, vividness your Lucid has. Also, there is no "official" way of classifying Lucidity, and these are just my interpretation. So remember that these levels are totally unrigid, and you may have aspects of multiple levels in your dream, as there are multiple factors, and it is up to you to determine how lucid you were. This list is a simplified generalization, and is not to be followed rigidly. Again, if you are Lucid you are Lucid, and the "levels" are just a way of describing how advanced of a Lucid you are having.

Non-Lucidity - You have no idea you are dreaming, and therefore are not Lucid. It doesn't matter how much control you have, how vivid or realistic the dream is, you aren't Lucid.

Low-Level Lucidity - You know you are dreaming, but you have very little or no control. The dream is most likely not vivid or realistic. The dream is not stable, and you probably wake up soon after attaining Lucidity.

Mid-Level Lucidity - You know you are dreaming, and have mild control, but you are not aware that you are invincibility and total power. The dream is probably mildly vivid and realistic. The dream is probably somewhat stable, and you will probably stay Lucid and in power for at least some time.

High-Level Lucidity - You know you are dreaming, and you have strong control over your surroundings, but are not in total power. The dream is vivid and realistic, but probably not lifelike. You are mostly stable, and you should be able to remain lucid and in control for a while.

Ultra High-Level Lucidity - You know you are dreaming, and have total control over the dream world. The dream is very vivid and realistic, most likely better than real life. You are fully stable, and can remain Lucid as long as you want until your body naturally wakes you up or leaves REM.

One final note on these levels. I do not speak from experience and never really achieved anything more than low-mid-level lucidity (see what I mean be mixing categories). I speak from knowledge gained spending time on this site, which I think is enough to write this, though I may edit it more as I gain experience.