guru

What exactly is a guru? And is a guru a necessary part of the path to enlightenment? The word comprises gu, which means darkness, and ru, which means the destroyer of that darkness. As with any great teacher, then, the guru is one who understands darkness and can also dispel the darkness by illuminating it. But what does that mean, exactly? Teachers arrive in many forms... books can illuminate the way. Any of my lovely yoga teachers are continually illuminating the path for all of their students. But does that make them gurus? My understanding of a guru includes the idea that this person possesses the ability to transmit energy to the student and, through this transmission, can dissolve spiritual ignorance or energetic blockages that prevent the student from understanding and dispelling the darkness they possess. So, by this standard, does that mean a person who can bestow shaktipat is necessarily one's guru? I have a friend who has received shaktipat twice now from a local shaman, but I don't think either of them view their relationship as that of guru and student. So what makes a guru more than just a teacher? And how does one determine whether they've encountered a guru? The Dalai Lama says to "rely on the teachings to evaluate a guru: do not have blind faith, but also no blind criticism."