Shiva Sutras

The Śiva·sūtras, technically akṣara·samāmnāya, variously called "", "pratyāhāra·sūtrāṇi", "varṇa·samāmnāya", etc., refer to a set of fourteen aphorisms devised as an arrangement of the sounds of Sanskrit for the purposes of grammatical exposition as carried out by the grammarian Pāṇini in the Aṣṭādhyāyī.
Pāṇini himself uses the term "akṣara·samāmnāya" whereas the colloquial term "Shiva sutra" is a later development, as per claims by Nandikeśvara in his Kāśikā, that the god Śiva sounded his drum fourteen times to reveal these sounds to Pāṇini. They were either composed by Pāṇini to accompany his "" or predate him.
Text and notation.
Each verse consists of a group of basic Sanskrit phonemes (i.e. either open syllables consisting either of initial vowels or consonants followed by the "basic" vowel "a") followed by a single 'dummy letter', or "anubandha", conventionally rendered in upper case and named " by Pāṇini.
Scheme.
This allows Pāṇini to refer to groups of phonemes with "", which consist of a phoneme-letter and an "anubandha" (and often the vowel "a" to aid pronunciation) and signify all of the intervening phonemes. "Pratyāhāras" are thus single syllables, but they can be declined (see Aṣṭādhyāyī 6.1.77 below). Hence the "pratyāhāra" "aL" refers to all phonemes (because it consists of the first phoneme of the first verse ("a") and the last "anubandha" of the last verse ("L"); "aC" refers to vowels (i.e., all of the phonemes before the "anubandha" "C": i.e. "a i u ṛ ḷ e o ai au"); "haL" to consonants, and so on.
Issues.
Note that some "pratyāhāras" are ambiguous. The "anubandha" "Ṇ" occurs twice in the list, which means that you can assign two different meanings to "pratyāhāra" "aṆ" (including or excluding "ṛ", etc.); in fact, both of these meanings are used in the "Aṣṭādhyāyī". On the other hand, the "pratyāhāra" "haL" is always used in the meaning "all consonants"—Pāṇini never uses "pratyāhāras" to refer to sets consisting of a single phoneme.
Combinations.
From these 14 verses, a total of 281 "pratyāhāras" can be formed: 14*3 + 13*2 + 12*2 + 11*2 + 10*4 + 9*1 + 8*5 + 7*2 + 6*3 * 5*5 + 4*8 + 3*2 + 2*3 +1*1, minus 14 (as Pāṇini does not use single element "pratyāhāras") minus 10 (as there are 10 duplicate sets due to "h" appearing twice); the second multiplier in each term represents the number of phonemes in each. But Pāṇini uses only 41 (with a 42nd introduced by later grammarians, "raṆ"="r l") "pratyāhāras" in the "Aṣṭādhyāyī".
Arrangement.
The Akṣarasamāmnāya puts phonemes with a similar manner of articulation together (so sibilants in 13 "śa ṣa sa R," nasals in 7 "ñ m ṅ ṇ n M"). Economy is a major principle of their organization, and it is debated whether Pāṇini deliberately encoded phonological patterns in them (as they were treated in traditional phonetic texts called Prātiśakyas) or simply grouped together phonemes which he needed to refer to in the "Aṣṭādhyāyī" and which only "secondarily" reflect phonological patterns. Pāṇini does not use the Akṣarasamāmnāya to refer to homorganic stops, but rather the "anubandha" "U": to refer to the palatals "c ch j jh" he uses "cU".
Example.
As an example, consider "Aṣṭādhyāyī" 6.1.77: "":
Hence this rule replaces a vowel with its corresponding semivowel when followed by any vowel, and that is why ' together with ' makes ". To apply this rule correctly we must be aware of some of the other rules of the grammar, such as:
Also, rules can be debarred by other rules:
Pratyāhāras.
Despite the possible combinations seen above, here are the 41 pratyāhāras in actual use by Pāṇini: