Upaniṣad (उपनिषद्)
Upaniṣad is a descriptive word with two upasargas, prefixes. One is upa, the other is ni; the word is sad (सद्). sad (सद्) is a dhātu, root, which is not used as a pada, word. It requires either a nominal or verbal suffix to become a word. For certain words, this suffix comes and goes away after converting the dhātu into a word. Here, the suffix, kvip, which is not visible, converts the root sad (सद्) into a word imparting the meaning of agent of action indicated by the root meaning. This root reveals the actions of viśaraṇa, wearing out, gamana, reaching, knowing and avasādana, putting an end to.
What is it that does these actions? That is indicated by the two prefixes, upa-ni. The prefix upa means something near. Brahman is never separate from you, it is you, but still, it is looked upon as something to be gained, to be known. If Brahman is me, what separates me from Brahman is ignorance. Ignorance about myself being Brahman makes me a seeker of Brahman. The prefix, upa, therefore, means Brahman, the very one sought after in life. You have to know for good what is meant by the prefix, upa, something that is close to you, that is sought after by you, that is yourself. That means, there is ignorance and therefore, knowledge is necessary. Because it is the truth of the knower, me, it is not the subject matter of other means of knowledge. It is phalavat (fruitful, yielding result) because it wears out and also puts an end to all undesirable things. Mere wearing out is not enough. The host of anarthas may revive and come back after sometime. Hence the other meaning of the root, avasādana, putting an end to, is also relevant. There is a positive gain too in this result. The knowledge makes you discover 'I am Brahman' positively.
The prefix, ni, means niścaya jñāna, clear knowledge, the knowledge that Brahman is indeed myself. Is the word 'knowledge' not enough? Where is the need for the adjective, niścaya, 'clear' here? In order to understand revelations such as "tat tvam asi, you are that", you have to get the vākyārtha, the meaning of the sentence. To see the meaning of that equation, 'you are that', you require to resolve many doubts through vicāra, inquiry. Therefore, you have got to ascertain what you know is correct. There the prefix, ni, is appropriately used.
The word upaniṣad means both self-knowledge as well as the text in the form of words that reveals this knowledge. The knowledge is upaniṣad and the book that conveys this knowledge is also upaniṣad. The upaniṣad is otherwise called Vedanta.
The subject matter of any upaniṣad is the same self-knowledge. If the subject matter is the same, why there are so many upaniṣads? They are all from the four Vedas. Suppose you are studying your branch of the Veda, it must have minimum one upaniṣad so that the vedic vision of you as Brahman is available for you. So we have upaniṣads in all the four Vedas. Each upaniṣad implies a teacher-student dialogue. Each teacher has his own way of looking at the whole thing; the Veda thus presents this subject matter from different standpoints through different upaniṣads. Certain topics may be emphasized in one upaniṣad while some other topics might be highlighted in others. Therefore, you see a few upaniṣads from different standpoints so that you understand the subject matter properly.
உபநிஷத் என்னும் பதத்தில் உப (சமீபம்), நி (அத்தியந்தமான, நிச்சயமான), ஸத் என்பவை அடங்கியிருக்கின்றன.
உப + நி + ஸாதயதி இதி உபநிஷத்(து). ஸாதயதி என்பது ஸத் என்னும் பகுதியினின்று பிறந்த வினைச்சொல். ஸத் என்னும் பகுதி விசரணம் (பிளத்தல்), கதி (அடைதல்), அவசாதனம் (நாசஞ்செய்தல்) ஆகிய மூன்று பொருள் கொண்டது.
மோக்ஷ இச்சையுள்ளவன் விஷயங்களின் மீதுள்ள ஆசையை ஒழித்து ஆசாரியரை அடுத்து அவரிடத்திலிருந்து கிரகிக்கும் வித்தையானது ஜீவாத்மாவை பரமாத்மாவுக்குச் சமீபமாய்க் கொண்டுபோய்ச் சேர்த்து அவித்யா பீஜத்தினின்றும் உண்டாகிய சம்சார விருக்ஷத்தை வேரோடு களைந்து பரப்பிரஹ்மத்தை அடையச்செய்து ஜனன மரண ரூபமான சம்சார துக்கத்திற்குக் காரணமாகிய அவித்தையை நாசஞ்செய்வதற்குச் சாதனமாயிருப்பதால், அந்த வித்தை உபநிஷத்(து) எனப்படும். இவ்வாறாக ஸத் என்னும் பகுதியில் அடங்கிய முப்பொருளும் உபநிஷத் சப்தார்த்தத்தில் விளக்கப்பட்டன. ஆகவே பிரஹ்மவித்தைக்கு உபநிஷத் எனப் பெயராயிற்று. இந்த வித்தையை உண்டாக்குகின்ற கிரந்தத்திற்கு உபநிஷத் எனப் பெயர் வழங்குவது உபசாரார்த்தமாம்.
