The most impressive uniqueness of the Sanskrit grammar is that, along with the Sanskrit language, it is unchanged in every age because it is a Divinely produced grammar. Its conjugation system, word formation and the style of poetry formation are all unique, unchanged and perfectly detailed since it appeared on the earth planet through the descended Saints. Take a line of the Yajurved,

There is a noun janah (people), and verb gacchanti (to go into) which is formed of gam dhatu (to go), like, gacchati, gacchatah, gacchanti. All the 90 conjugations of the verb gacch (to go) and all the 21 forms of the noun jan (people) are used in the same way without any change in the Vedas, in the Puranas and in other Sanskrit literature as well, because they are ever perfect without any sound shift. The Sanskrit language represents the literal form of the Divinity on the earth planet. Such is the Sanskrit grammar.