First we will see the meaning of the word
There are three terms
Brhadvaad brhad - brhad means great
It is great qualitatively & quantitatively - size & content
[But so is Chandogya (same size) - but greatness of brhad is not only is it big in size but also it is greatest in content.]
All important ideas contained in all other Upanishads is contained in this Up -& many ideas here are not found in any other Upanishad - hence its greatness
It is studied in aranya forest - indicates sannyashrama after renouncing everything aranya anuchamanatvat
Brahmana portion of Vedas corresponds to karma grhastashrama
Aranyaka portion of Vedas corresponds to upasanas vanaprasthashrama
Upanishad portion of Vedas corresponds to brahmavidya sannyasashram
Idea is by the time a person has followed an ideal Vedic life he has attained sufficient maturity which is measured or indicated by detachment
Only a mature detached mind can grasp the teaching
Upanishad - brahmavidya/
upa + ni + sad
Upa : method for gaining brahmavidya
Guru upa sadanam - approaching a teacher with reverence faith & humility
Guru sastra pramana dvaram prapti
Ni : conditions for gaining brahmavidya
Knowledge needs to be ni-schyatmaka -apratibadha jnana or jnana nishta
free from doubt (intellectual) &
free from habitual complexes (mental or emotional)
Even we are intellectually sharp to grasp if we are not emotionally mature, if we are not free from emotional complexes such as anger frustration depression etc. then this knowledge is not complete. These complexes are turned turned termed viparya pratibandhaa.
Hence we have shravana mañana & nidhidyasana for these 3 respectively
Sad : avasadayati iti sad. Destroyer of ignorance of Brahman which alone is cause of samsara. So 2 fold destroyer - directly of avidya & indirectly of samsara.
(Sad also has a meaning of reaching or leading to : gamayati leading unto Brahman which is of the nature of ananda)
Sad is the benefit of brahmavidya
Since Upanishad is prama & pramana is shabda pramana alone the shabda or Scripture itself is called upanishad
Primary meaning of upanishad is the knowledge obtaining n the mind vrtti jnanam eva upanishad padasya mukhyartha
Secondary meaning is the scripture that is the shabda pramana or means of such knowledge
BU belongs to Shukla Yajur Veda
SYV has 2 branches - Kaanva & Maadhyamdina
The version of this Up which Shankara has written his great bhashyam is in Kaanva Shaka
(Sw Vidyaranya has written a independent bhashyam on the Maadhyamdina Shaka )
This Up is divided into 3 parts called kaanda
Upadesha teaching is the primary aim; called Madhu kanda because here Brahman is revealed as the adhistanam of the relative or interrelated world. For this the Up discusses the interdependence of the world - upakarya upakaraka bhava - which is revealed by a technical word "Madhu"
Muni kanda or Yajnavalkya kaanda
Theme here is upapatti reasoning; providing logical support & showing the propriety of the teaching
Throughout third portion the teacher is Yajnavalkya
Another name for Yajnavalkya is Vaajasaneyaha - because his Guru is Surya Bhagwan & one of the names for Surya is Vajasanihi - Vajas means annam and sanihi means one who gives. Vaajasaneyaha's teaching (this kaanda) is also called vajasanehi samhita.
Theme is variety of upasanas. Term khila means compilation. Different upasanas are compiled.
Each Kanda is divided into 2 adhyayas - so total there are 6 chapters. Each adhyaya is divided into sections called brahmanam (similar to valli in KathaUp)
Among the 10 Upanishads Adi Shankara's bhashyam here is the greatest & most extensive - he excels here & his bhashyam here is without parallel in any other upanishad - it appears to be his favorite upanishad
Many secondary commentaries have arisen on AS bhashyam - most famous is Sureshwaracharya,'s - brhad vartika or vartikamrtam. Sureshwaracharya has the name vartikakaara as he has written many vartikas (Taitt Up) but BU vartika is his greatest work with 12,000 verses! Many commentaries have been made on this vartika - vartika Sara - a condensed commentary on the vartikas has been written by Vidyaranya.