ac sandhi

ac sandhi is the general name for sandhi changes that involve two vowels. For example, the rule we studied in the previous lesson is an example of ac sandhi:

ac sandhi has many rules of varying importance. Some are truly minor, and others are important general patterns. Here, we will focus on the important general patterns and complete our basic picture of ac sandhi.

But there is also an important issue we should address: rule 6.1.77 has a serious flaw. In Sanskrit, two similar vowels should combine and become long:

But rule 6.1.77 will produce an error:

So in addition to completing our basic picture of ac sandhi, we will also ensure that our system handles the example above correctly.

As in the previous lesson, the rules below will borrow context from the adhikāra rule 6.1.72:

ec as first vowel

Once we understand rule 6.1.77, we can easily understand 6.1.78:

So we get sandhi changes like this:

Rule 6.1.78 is nice and simple. Now let's turn to the rules where a is first:

a as first vowel

In Sanskrit, a will combine with most vowels to form a compound vowel:

Here, one vowel (et) replaces two vowels (āt and it). How might we model this behavior with our rules?

Pāṇini approaches this problem by creating a new adhikāra rule:

What does this rule mean? Recall that we represent “previous” terms with the fifth case and “following” terms with the seventh. So, what this rule means that in the scope of this adhikāra rule, terms in the fifth and seventh case are both replaced with a single item.

With this context in place, we can model what happens when a is the first vowel. In general, the change is simple:

But if the second vowel is a compound vowel, we use a slightly different rule:

The terms guṇa and vṛddhi will be very important later on.

Substitution with the closest option

Unfortunately, rules 6.1.87 and 6.1.88 have a problem that we've seen before: these rules tell us to use a guṇa or vṛddhi vowel, but they don't specify which one. We know what the correct result should be, but the rule allows some clearly incorrect results:

So Pāṇini offers this rule to help us perform the correct substitution.

Roughly, “closeness” refers to properties like places of articulation, semantic meaning, and the like. In the context of the rules above, we can examine the points of articulation that these vowels use.

If we return to our example above, ā is pronounced at the soft palate and i is pronounced at the hard palate. e uses both of these points of articulation. o uses the soft palate and the lips. So e is a closer substitute than o. And likewise, o is better if the combination is a and u:

Addition of r

The rules above seem to work as intended. But if we test this rule against our Sanskrit knowledge, we find another problem. In Sanskrit, ṛ has no compound vowel. Instead, it combines with a with some help from the semivowel r:

But with our current system, rule 6.1.87 (ād guṇaḥ) can hardly function. at seems like the closest guṇa vowel, but this produces a bad result:

The fix is another rule about how to perform a substitution:

And with this rule in hand, we can perform the substitution correctly and get the desired result.

Two similar vowels

Finally, we can return to the example from the start of this lesson and complete our basic picture of vowel sandhi. Recall the example we wish to model:

To handle this special case, we just need a new rule:

The meaning of this rule is clear. And with rule 1.1.51, it is also clear what the result should be for each vowel:

Review

With just a few short rules, we have fully characterized the basic patterns of ac sandhi. This is the power the Pāṇinian system gives us.

In the next lesson, we will finish our survey of sandhi and look at some examples of sandhi involving consonants. These rules are part of an unusual section of the Aṣṭādhyāyī and have some special properties.