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- Before you begin
- Similar Vowels
- Disimilar Vowels
- Special Rules of Internal Sandhi
- Special Rules of External Sandhi
This page covers the rules of vowel sandhi. Any rule in which the first letter is a vowel is considered a vowel sandhi rule. If you prefer charts over sentences, you can use the charts at the bottom of the page. As far as I am aware, this page contains every rule of vowel sandhi. Pre-Classical works don't always conform to these rules.
Before you begin
All of the rules below describe changes between two vowels, unless otherwise described. A vowel in front of a consonant will not change, unless otherwise described. The two vowels must be right next to each other with no letters between them.
The basic principle of vowel sandhi
Two vowels should not be next to each other.
Early Sanskrit probably had vowel sounds like you see below:
A knowledge of these old vowels will simplify the rules below. Over time, the old vowel sounds merged to become the ones we know today:
Similar vowels combine and become long. Remember, compound vowels are dissimilar to everything.
भव अर्जुन → भवार्जुन
bhava arjuna → bhavārjuna
दग्ध अरण्य → दग्धारण्य
dagdha araṇya → dagdhāraṇya
सु-उक्त → सूक्त
su-ukta → sūkta
Two dissimilar vowels will change based on the first vowel.
If the first vowel is -a or -ā, then the first vowel combines with the second and strengthens it by one level. If the second vowel is already strong, then the first vowel disappears.
राज इन्द्रः → राजेन्द्रः
rāja indraḥ → rājendraḥ
महा ऋषिः → महर्षिः
mahā ṛṣiḥ → maharṣiḥ
हित उपदेशः → हितोपदेशः
hita upadeśaḥ → hitopadeśaḥ
तस्य औदार्यम् → तस्यौदार्यम्
tasya audāryam → tasyaudāryam
Otherwise, the first vowel will change to its corresponding semivowel. First, some examples for simple vowels:
इति आह → इत्याह
iti āha → ityāha
अपि अस्य → अप्यस्य
api asya → apyasya
मधु इव → मध्विव
madhu iva → madhviva
Now, some examples for compound vowels. For compound vowels, the second part of the first vowel becomes the semivowel. Remember that e, ai, o, and au are treated as *ai, *āi, *au, and *āu for historical reasons.
भोअति → भवति
bhoati → bhavati
जेअति → जयति
jeati → jayati
सह नौ अवतु → सह नाव् अवतु
saha nau avatu → saha nāv avatu
Compound vowels have some exceptions in external sandhi.
Special Rules of Internal Sandhi
The following simple vowels will frequently change as follows:
- First vowel
- i, ī
- u, ū
धी + इ → धियि
dhī + i → dhiyi
भू + इ → भुवि
bhū + i → bhuvi
गॄ + अ + ति → गिरति
gṝ + a + ti → girati
ṛ and ṝ
ṛ, when after a single consonant, becomes ri before y-.
कृ + य + ते → क्रियते
kṛ + ya + te → kriyate
ṝ in front of a consonant suffix becomes īr. But if the ṝ comes after a letter in pavarga, then it becomes ūr instead. Note that this change applies only when the second letter is a consonant.
गॄ + य + ते → गीर्यते
gṝ + ya + te → gīryate
पॄ + न → पूर्न
pṝ + na → pūrna
For compound vowels, the second part of the first vowel becomes the semivowel when it is followed by a vowel. The change also occurs when the second letter is the consonant y. (This change occurs because many of the y consonants in Classical Sanskrit come from i vowels in Vedic Sanskrit.)
गो + यः → गव्यः
go + yaḥ → gavyaḥ
Special Rules of External Sandhi
A prefix ending in a or ā, when in front of a verb starting with ṛ, combines to form ār.
उप ऋच्छति → उपार्च्छति
upa ṛcchati → upārcchati
If the verb starts with a vowel, then the a prefix, which is used to mark the past tense, will combine to make the vowel strong.
अ + इच्छ + त् → ऐच्छत्
a + iccha + t → aicchat
Also, pra + ūḍha becomes prauḍha.
For compound vowels, the second part of the first vowel becomes the semivowel when it is followed by a vowel. But in external sandhi, the semivowel is dropped for e and ai. The next rule features an exception to this one.
नगरे इह → नगर इह
nagare iha → nagara iha
रथोपस्थे उपाविशत् → रथोपस्थ उपाविशत्
rathopasthe upāviśat → rathopastha upāviśat
When -e is in front of a-, the first vowel stays the same and the a- disappears. Note that the letter a is removed because of the influence of the complex and common e vowel.
ते अब्रुवन् → ते ऽब्रुवन्
te abruvan → te 'bruvan
Words unaffected by sandhi
The words below will not combine with the words that follow them:
Particles of interjection (he, aho, …) and particles that consist of just a single vowel (ā, i, u, …):
इ इन्द्र → इ इन्द्र
i indra → i indra
हे अर्जुन → हे अर्जुन
he arjuna → he arjuna
The vowels ī, ū, and e, when they end a word in the dual:
नगरे अहं पश्यामि → नगरे अहं पश्यामि
nagare ahaṃ paśyāmi → nagare ahaṃ paśyāmiI see the two cities.
नगरे अहं पश्यामि → नगरे ऽहं पश्यामि
nagare ahaṃ paśyāmi → nagare 'haṃ paśyāmiI see in the city.
and amī, the plural form of asau.
Other exceptions can be found in Panini's Ashtadhyayi (1.1.11 - 1.1.19; see my translation of these rules here).
First Vowel Second Vowel a/ā i/ī u/ū ṛ/ṝ e ai au ā ya va ra e ' ā a āva a ā yā vā rā a ā ā ā āvā ā e ī vi ri a i ā i āvi i e ī vī rī a ī ā ī āvī ī o yu ū ru a u ā u āvu u o yū ū rū a ū ā ū āvū ū ar yṛ vṛ ṝ a ṛ ā ṛ āvṛ ṛ ar yṝ vṝ ṝ a ṝ ā ṝ āvṝ ṝ ai ye ve re a e ā e āve e ai yai vai rai a ai ā ai āvai ai au yo vo ro a o ā o āvo o au yau vau rau a au ā au āvau au