_Om_ is denominated a word (शब्द) in the Veda and other sacred scriptures, and explained as a noun also (संज्ञा) in the Nirukta and other lexicons. It is derived in the Koshas from the root _aba_ or _ava_ to protect, or save (रक्षणे) with the _Unadi_ suffix मन् an anomalous formation into _om_ to denote “protection.” Dr. Mitra too derives it from the radical अब “to preserve” with the suffix मन to denote the Most High according to Manu and Gítá. (Translation of Ch’hándogya Up. p. 4). [Sidenote: 4. Its Primary sense धात्वर्थः] Apart from the symbolical significations of _Om_ (of which there are several as we shall come to notice afterwards), its primary and literal sense would make us give different interpretations of it according to the derivation of the term both in its verbal and nominal forms. अव as a verb in the imperative mood means “save” as मातरब​, त्रातरब​, दबऽब &c. in the _Mugdhabodha_, corresponding with the expressions, _Ave Maria_, salve salvator, salve Deus, save O God &c. [Sidenote: 5. Its Nominal sense ब्युत्पत्यर्थ] But _aba_ to protect or preserve gives us the nominal (कृदन्त) forms of aba, ába, ábu, and ábuka (अब, आब, आबु, आबुक​), meaning a father or preserver in the Prákrit Speech of Sanskrit dramas, and these are found to agree in both respects of sound and sense with the words _áb_, _ábá_, _ábu_, _ábuka_, _abi_ as _ábuka_ &c. in Hebrew, Chaldee, Syriac and Arabic languages. This gives us the original meaning of अब of which ॐ is a derivative form, and shows the close affinity which the Aryan root bears to the Semitic, both in its sound and signification of “Father” (पाता and पिता) applied to the Great God. [Sidenote: 6. The word Om ॐ शब्दः ।] But our question being _Om_ and not the root अब, we ought to know to what part of speech it belongs and what sense we are to give of it here. It is said to be a word indicative of auspiciousness when used at the beginning; (आदौ ॐ शब्द प्रयोगो माङ्गलिकः). But whether as a verb or noun or any other part of speech, we know nothing of, and we are utterly at a loss what word to substitute for it in its translation. This is the reason why the word _Om_, is used by itself in the translations of Sanskrit works by Europeans and our countrymen also for want of a proper term, as it is seen in the English versions of Vedas and Upanishads. [Sidenote: 7. An aptot noun अब्यय शब्दः ।] _Om_ is enlisted as an indeclinable word in grammar having no inflection of its own in gender, number, case or person, and agreeing with all words in its unchanged state, as in the examples:— ओमीश्वर, ॐ दुर्गा, ॐ ब्रह्मन्, ॐ देबेभ्यो जुहोमि, ओमुपेत्वा ऊर्जेत्वा &c. It is included in the (स्वरादिगण) as an aptot noun, and with indeclinable particles (निपातन), as an adverb, conjunction and interjection also with various significations. [Sidenote: 8. The initial _Om_ आद्योमार्थः ।]