External Consonant Sandhi

Also known as: hal-sandhi

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This page covers the rules of external consonant sandhi. These rules describe changes between two words when the first letter is a consonant.

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

The Principle

Consonants will change to make things easier to say.

Given this rule, I strongly encourage you to speak these changes out loud.

Simplifying Words

All nouns that end in consonants must go through a two-part simplification:

  1. All extra consonants are removed from the end of the word until there is only one left (with one exception).

  2. The remaining consonant is reduced.

Removing extra consonants

A word cannot end in a consonant cluster, with one exception. First, some examples of the general rule:

Now, the exception. If r appears in front of a stop consonant, and if the stop is not part of some suffix, then the stop remains.

Reducing to Eight Consonants

In external sandhi, all words that end in consonants must have their consonants reduced to one of these eight.


To reduce a consonant, follow the steps below from top to bottom:

Stops become unvoiced and unaspirated.

c, ś, and h are converted to k. If the c was a j before this reduction started, it might become instead.

ñ becomes .

becomes .

s and r are replaced by the visarga.

The letters that have not been considered here (ṇ, y, l, v) will never appear at the end of a word.

Special rules for words ending in aspirated letters

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

This rule also exists in internal sandhi, with a few extra rules.

Rules for final stops

All final stops will take the voice of the letter that follows them. Vowels are voiced sounds.

The four final stops (k t ṭ p) become the nasal sound from their varga when followed by n or m.

Extra rules for t

t becomes c in front of all hard palate consonants (c, ch, j, ch, ñ, ś) and becomes in front of ṭ, ṭh, ḍ, or ḍh (not ). This result, by our general rule, takes the voice of the letter that follows it.

Rules for n

Second Letter
c, ch
ṃś —
ṭ, ṭh
ṃṣ —
t, th
ṃs —
j, jh, ś
ñ —
ḍ, ḍh
ṇ —
m̐l (ṃl) —
other letter
n —

Rules for m

When -m is in front of a consonant, it becomes the anusvāra. Otherwise, it stays m.

Rules for

Click here to read about visarga sandhi.

Changes in the Second Letter

The changes below are applied after the first letter has already changed. Remember, the term second letter refers here to the first letter of the second word:


ch can become cch after any vowel. It always becomes cch when either of these things is true:

n and are doubled when both of these things are true:

The letter h-

In front of h-, the four final stops (k t ṭ p) become voiced. The h- becomes the voiced and aspirated version of the final stop.

The letter ś-

ś- becomes ch when both of these things are true:

ś- can become ch after k, ṭ or p, but the change is rarely made.