'Basic' grammar in Sanskrit may be an oxymoron, but here are some fundamentals.
Sanskrit is an inflected language, meaning that the nouns are declined and the verbs are conjugated.
The Sanskrit language tends toward the subject-object-verb word ordering, but does allow for multiple type of sentence formulations particularly in the sutra form.
There are three principal numbers used in the inflection of the Sanskrit language. These are singular, dual, and plural.
In declining Sanskrit nouns, there are eight cases used. These are nominative, vocative, accusative, instrumental, dative, ablative, genitive, and locative.
Nouns are declined according to their endings, with the exception of pronouns which have specific declensions.
The short a declension: