In ancient Sanskrit grammar, what is the name of the foundational treatise written by Panini that systematically describes the structure of the language?

Introduction / Context:
This question belongs to classical Indian scholarship and linguistics. It asks about the key grammatical work composed by Panini, which is considered one of the most scientific treatments of language in ancient times. Knowing the title of this treatise is important for general knowledge about Sanskrit and the history of grammar.

Given Data / Assumptions:

• The author in question is Panini, an ancient Sanskrit grammarian.
• He wrote a systematic book on Sanskrit grammar.
• Four titles from different traditions are given as options.
• Only one of them is correctly associated with Panini grammar.

Concept / Approach:
Panini most famous work is called "Ashtadhyayi", which literally means "the book of eight chapters". It lays down concise rules or sutras describing Sanskrit phonetics, morphology and syntax. "Mahabhashya" is a major commentary by Patanjali, "Mitakshara" is a legal commentary and "Madhyamika Karika" is a text associated with Buddhist philosophy. Recognising these distinctions makes it easy to identify the correct answer.

Step-by-Step Solution:
Step 1: Recall that Panini is credited with composing the Ashtadhyayi, a compact but powerful grammar of Sanskrit. Step 2: Understand that this work is organised into eight chapters, each containing many short rules or sutras. Step 3: Compare the options. Mahabhashya is not by Panini; it is a later commentary on his work. Mitakshara is about law and inheritance, while Madhyamika Karika is philosophical. Step 4: Since only Ashtadhyayi matches Panini authorship and a grammatical theme, it must be the correct choice. Step 5: Select option "Ashtadhyayi".

Verification / Alternative check:
Standard histories of linguistics and Sanskrit literature clearly describe Ashtadhyayi as Panini masterpiece. They also mention that later scholars like Patanjali wrote commentaries, which confirms that Mahabhashya, though related, is not his original grammar text. This cross reference supports the selection of Ashtadhyayi as the only accurate option.

Why Other Options Are Wrong:
Mahabhashya is a great commentary on Panini grammar, not the grammar itself. Mitakshara belongs to Hindu law and is attributed to Vijnaneshwara. Madhyamika Karika is connected with Nagarjuna and Buddhist philosophy. These works are important but belong to different authors and subject areas, so they do not answer the question asked about Panini treatise.

Common Pitfalls:
Because Mahabhashya and Ashtadhyayi are both linked to grammar, learners sometimes confuse them. The safe method is to remember that Ashtadhyayi is the original systematisation created by Panini, while Mahabhashya is a later detailed commentary by Patanjali. Keeping this hierarchy clear in mind will help in many similar questions on ancient Indian texts.

Final Answer:
Ashtadhyayi