What is Saptamī vibhakti

सप्तमी विभक्ति or Locative Case of the noun-form represents the "where" of the sentence.
In other words locative case represents the locative of the sentence.

Let us look at the following sentences to understand this.

Saptamī Vibhakti sentences in Sanskrit

1. सः नगरे वसति (He lives in the city)
In this sentence, नगरे is the locative of the sentence.

2. शिशुः शज्यायां शेते (Child sleeps on the bed)
In the above sentence, शज्यायां is the locative of the sentence.

In sentence 1 above, if we ask the question, 'where does he live?' the answer that we get is 'city'.
In sentence 2 above, if we ask the question, 'where does the child sleep?' the answer that we get is 'bed'.
So, in general, answer to the question 'where' is the locative of the sentence.

Examples of Saptamī Vibhakti in Sanskrit

Saptamī Vibhakti of Ram

विभक्ति	एकवचन	द्विवचन	बहुवचन
प्रथमा	रामे	रामयोः	रामेषु

Saptamī Vibhakti of Lataa

विभक्ति	एकवचन	द्विवचन	बहुवचन
प्रथमा	लतायाम्	लतयोः	लतासु

Saptamī Vibhakti of Fal (Phal)

विभक्ति	एकवचन	द्विवचन	बहुवचन
प्रथमा	फले	फलयोः	फलेषु