What all must be studied for complete study of grammar of Sanskrit ? One general impression is that one should study and then the job is done. But there is a श्लोक
अनधीते महाभाष्ये व्यर्था सा पदमञ्जरी ।
अधीते तु महाभाष्ये व्यर्था सा पदमञ्जरी ॥
Here, the word पदमञ्जरी usually refers to अष्टाध्यायी by पाणिनि. So, here we have reference to two books – अष्टाध्यायी by पाणिनि and महाभाष्य by पतञ्जलि respectively. Original of the two is अष्टाध्यायी by पाणिनि, though, in this श्लोक more credence is accorded to study of महाभाष्य by पतञ्जलि.
However in his सिद्धान्तकौमुदी, भट्टोजी दीक्षित pays his tributes as मुनित्रयं नमस्कृत्य. This seems to be so, because Sanskrit grammar is itself known as त्रिमुनि-व्याकरणम्. The त्रिमुनि-s are पाणिनि, वररुचि कात्यायन and पतञ्जलि Contribution of वररुचि कात्यायन is by his वृत्ति-s, which often explain सूत्र-s in अष्टाध्यायी by supplementary सूत्र-s, as if अष्टाध्यायी becomes more complete by the supplementary सूत्र-s in वृत्ति-s of वररुचि कात्यायन. Because of his वृत्ति-s वररुचि कात्यायन is also known as the वार्त्तिक (वृत्तीनां कर्ता).
अष्टाध्यायी is the base both for महाभाष्य by पतञ्जलि and वृत्ति-s of वररुचि कात्यायन. That is why it is said in the above श्लोक, that if one studies महाभाष्य, there is no need to study अष्टाध्यायी separately.
Actually language has two aspects – (1) words and (2) using the words to make a meaningful expression. The second part “using the words to make a meaningful expression” often becomes the exercise of composing a sentence.
From what I have understood, अष्टाध्यायी’s focus is on words, rather on formatting of words. This is so, because in Sanskrit every word to be used in a sentence, rather, for any word to be worthy of use in a sentence, it has to be a formatted word.
Second aspect of Sanskrit is freedom from syntax. In Sanskrit the formatting of words makes the words so much self-same, that they can be placed anywhere, in any sequence or order. Although the word order is most commonly the Subject-Object-Verb (SOV) order, that is not any rigid word order.
Formatting of words is best detailed in अष्टाध्यायी. But study of अष्टाध्यायी should not be understood as study only of the eight chapters, four quarters of each chapter. There are important परिशिष्ट-s, which are part and parcel of अष्टाध्यायी. They are गणपाठः, धातुपाठः, लिङ्गानुशासनम्, उणादिसूत्राणि, फिट्सूत्राणि, पाणिनीया शिक्षा.
Most books on अष्टाध्यायी detail सूत्राणि in the thirty-two quarters in अष्टाध्यायी. But to make the study of Sanskrit grammar complete, one must study also all the परिशिष्ट-s.
One method of study has been as propounded in his सिद्धान्तकौमुदी by भट्टोजी दीक्षित. But सिद्धान्तकौमुदी is said to be a composition of 17th century, just about 400 years old. There certainly have been many studies of अष्टाध्यायी, evidenced by many commentaries, called as वृत्ति-s, some well-known among them being काशिका-वृत्तिः, न्यासः, मनोरमा, बाल-मनोरमा, प्रौढ-मनोरमा, तत्त्व-बोधिनी, etc.
Although Sanskrit offers quite some freedom of syntax, there have been some definite concepts of composing sentences. These are possibly best detailed in वाक्पदीयम् of भर्तृहरि, said to be step brother of राजा विक्रमादित्य of 5th AD.
Another aspect of Sanskrit language, which is considered as part of its grammar is adorned speech, adorned by rhythm or by fancy.
- Adornment of speech by rhythm is covered in study of prosody छन्दःशास्त्रम्, also called as शब्दालङ्कार.
- Adornment of speech by fancy is covered in अर्थालङ्कार.
As mentioned earlier, every word to be worthy of use in a sentence needs to be formatted. In formatting there is morphology through different steps called as प्रक्रिया. There have been studies focusing only on the morphological aspects of formatting of words and are available in books such as प्रक्रियासर्वस्वम्.
Actually etymological studies व्युत्पत्तिविचार may be considered as the converse of morphological studies. But etymological studies can go deeper than just the converse of morphological studies. I came across a book व्युत्पत्तिवाद published by राष्ट्रिय संस्कृत संस्थानम् http://www.sanskrit.nic.in/DigitalBook/V/Vyutpattivada_2016.pdf
One more aspect of study of words is study of synonyms and antonyms. Sanskrit has a great old tradition of such study. Two such studies which are monumental, are निघण्टु-निरुक्त by यास्काचार्य and अमरकोश (actual name नामलिङ्गानुशासनम्) by अमरसिंह.
I hope this compilation becomes useful to anyone wanting to undertake comprehensive study of grammar of Sanskrit.