An Introduction to Sandhi

Every language has a set of sounds that is used to make words and sentences. Usually, the sounds are quite easy to pronounce, especially for native speakers. But even though the sounds might be easy to say when they're separate, it can be quite difficult to say some of them when they're put together, especially when speaking quickly! Sanskrit speakers faced these exact problems, and they did what people everywhere did with their own languages: in one place or another, they started to simplify their pronunciation. These simplifications did not happen everywhere, but they certainly did in ordinary speech. The early Sanskrit grammarians, trying to study their own language and preserve it for the future, gave a single name to the set of all of these changes: sandhi.

The word "sandhi," more properly written as saṃdhi, means "junction" or "combination." It refers to the "combination" of two sounds that sit next to each other. The word "sandhi" was borrowed into English, where it refers to the same sorts of changes in any language. So, we can talk about English sandhi, Chinese sandhi, Latin sandhi, and so on.

The concept of "sandhi" might seem strange to you. Fortunately, English shows some signs of sandhi rules. For example, consider three English words that are borrowed from Latin: "indirect," "impossible," and "illuminate." Each of these words starts with "in," but the "n" of this "in" has changed to more closely match the letter that follows it. Note that the pronunciation and spelling of these words have both changed. The same thing happens in Sanskrit, and if sandhi is applied in a text, we must write out all of the changes.

In the oldest parts of the Vedas, sandhi changes do not uniformly occur. That is, a change can appear once in one sentence and not at all in the next. But in the later form of the language — the form that we're studying right now — the grammar of the language is more consistent. With the rare exception, all Sanskrit texts apply the sandhi rules.

Our first sandhi rules

All sandhi rules are of two types. Rules about changes between words are called external sandhi rules. Rules about changes within a single word are called internal sandhi rules. External sandhi is essentially an extension of internal sandhi. Almost all of the rules are straightforward, and you shouldn't have much trouble with them.

Unfortunately, though, many people think that sandhi is overwhelming and frustrating. Some students find sandhi so difficult that they stop learning Sanskrit. But sandhi has been made difficult because it has not been taught well. In fact, most of its rules are very straightforward. Even the most complex ones can be reduced to a few simple ideas. For instance, this simple idea is the reason for all of the sandhi changes between vowels:

To make things easier to say, two vowels should not be next to each other.

We can apply this principle right now. Consider a simple verb, like gacchati. What will happen to its final vowel if we put it in front of another noun? If the noun starts with a consonant, there's no problem — we don't have to make any changes. But otherwise, the vowel will change. Take a look at the rule below:

Two similar vowels combine to form the long form. (Remember that only the simple vowels can be similar to each other. A compound vowel is dissimilar to everything.)

See, this change is quite simple — it's even a little fun! Notice that gacchatīśvaraḥ is much easier to pronounce that gacchati īśvaraḥ. Also note that these two words are now written as one, both in Devanagari and in IAST.

But what happens if the second vowel is not similar to the first one? Well, we have two situations to consider here:

If the first vowel is a simple vowel, then it follows this rule:

If the first vowel is neither a nor ā, then it becomes a semivowel. (More specifically, the first vowel becomes the semivowel that corresponds to it. So, i and ī become y, and become r, and so on.)

See, sandhi is quite simple after all! Certainly, there are other rules that are trickier than the ones shown here. But, almost all of them can be simplified just like this.

Note that a and ā aren't considered in this rule. That's because these two vowels don't have a semivowel that they can change into. a and ā follow a different (but still easy) rule, and we'll study that rule later in the guide. Also, note that the two words are not written as one in the example above. Usually, they are; but in this unit, let's keep them separate. Sandhi can be a scary thing, and it's best to make things easier for now.


Although sandhi is not very difficult, it does take some time to get used to. For that reason, the next few lessons will not feature any new Devanagari. Devanagari lessons will resume in the lesson on case 2.


In this lesson, we've learned the following terms:

The term for the set of sound changes that governs a language.
external sandhi
The term for sandhi changes between words
internal sandhi
The term for sandhi changes within a single word