He who dispels the darkness called spiritual ignorance (ajnana) from within us and bestows upon us the light of spiritual knowledge is addressed as Guru or Sadguru. He is the Spiritual Guru.

The two syllables, Gu and Ru are very powerful and significant. Every syllable used in our scriptures is very important. On Guru Purnima, such Guru is worshipped.

Not just in Kali Yuga, in any Yuga (eon), one cannot do without a Spiritual Guru. Even if you are not spiritually inclined, you will agree that you need a Guru (a teacher) to learn any trade. Without a Guru or a teacher, one cannot learn anything. Even Saint Tyagaraja expressed this sentiment in one of his compositions wherein he says- knowledge pursued without Guru is futile.

(Q&A, USA, 29 Jul 2011)