Internal Consonant Sandhi

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This page covers the rules of internal consonant sandhi. Internal consonant sandhi acts within a single word. Any rule in which the first letter is a consonant is considered a consonant sandhi rule. Some of the rules have charts, which you can see at the bottom of the page.

As far as I am aware, this page contains every rule of internal consonant sandhi. Pre-Classical works don't always conform to these rules.

General Rules

Internal and external consonant sandhi

The internal consonant sandhi rules and external consonant sandhi rules have many rules in common. The best way to think about the rules on this page is as "exceptions" to the normal external consonant sandhi rules. So, when you apply consonant sandhi, you should first check for the exceptions mentioned on this page; and if there aren't any that apply, you should use the external consonant sandhi rules.

No sandhi near certain letters

When the second letter letter is a vowel, a nasal, or a semivowel, no sandhi change of any kind will occur, with only a few exceptions.

Here are some examples of the general rule:

Assume that all rules follow this principle. Those that do not will be clearly labeled.

Aspirated Letters

These rules apply to the first letter.

General Rule

Aspirated letters become unaspirated.

Exceptions for -h

h is treated like gh when either of these things is true:

In other roots, h does all three of these peculiar things:

Four exceptions are snih, muh, nah and dṛh.

Moving the aspirate backward

A piece's first letter will become aspirated if all of these things are true:

The fourth requirement is for internal sandhi only. The other three are the same as in external consonant sandhi.

Moving the aspirate forward

t- and th-, when they are the second letter, become dh-.

One exception to this rule is the root dhā, which becomes dhat in this situation.

Letters from cavarga

Final j

By the external sandhi rules, c always reduces to k. But j is more irregular. It usually becomes k, but it can also become or .

Final ś

A final ś changes in these ways:


prach is treated like praś. In external sandhi and ātmanepada, it becomes praṭ.

Changing n- to ñ-

Final c and j change n- to ñ-.

Retroflex letters

A retroflex letter, if followed by a tavarga letter, shifts it to ṭavarga.

becomes k when followed by s.

Final n and m

Final n becomes the anusvāra if both of these things are true:

Final m becomes n in front of v.

Final s

A final s changes in one of two ways:

s changes to t

The s in vas and ghas becomes t when in front of the s of a verb suffix.

s also becomes t in some parts of the reduplicated perfect.

s disappears

s disappears when in front of d or dh.

Special Rules

These rules will always apply, with only a few extremely rare exceptions. The exceptions can be counted on one hand.

n → ṇ

The idea is this. The four sounds in the first line will leave the tongue in the retroflex position. The tongue stays there for the vowels, kavarga, pavarga, and some other sounds, and it will stay there unless any other sound is spoken. If nothing causes the tongue to move, then the third line comes into play.

s → ṣ

Exceptions are hiṃs and puṃs.


Special Principles

Change Cause Condition 1 Condition 2
n → ṇ Any retroflex sound that is not a stop consonant (ṛ, ṝ, r, ṣ) One of these four letters appears in front of n. The two letters may be separated by any of the following: vowels, letters from kavarga and pavarga, h, y, v, or the anusvāra n is followed by a vowel, m, y, v, or another n.
s → ṣ k, r, and any vowel apart from a and ā (i, ī, u, ū, ṛ, ṝ, e, ai, o, au) One of these ten letters appears in front of s. The two letters may be separated by a visarga or anusvāra s is not followed by r.