णत्वम्/अनुस्वारप्रयोगः Na and Anusvar usage

अनुस्वारप्रयोगः Anusvara Usage

When to write anusvara and when to write म् (m)?

Anusvara is a pure nasal pronunciation sound. It can not be pronounced independently. It can follow only a vowel and not a consonant. In devanagari script, it is represented by the symbol . (dot/small circle) on top of the vowel (or the compound consonant ending in a vowel).

म् has the labial position in conjunction with nasal - meaning air passes through nose and mouth. The air through mouth is stopped by closing the lips.

1. When a word ends in म्, if there is no other word after it, then म् should be written (as only म् can be pronounced in that case, and anusvara cannot be pronounced).
   For example: गृहम्
2. When a word ends in म् and we want to pronounce the next word in the same sentence after a  pause, then म् remains at the end of the first word.
   For example: गृहम् गच्छति
3. When a word ends in म्, and we want to pronounce the next word in the same sentence without a  pause, then: 
1. If the next word starts with a vowel, then म् remains at the end of the first word.
   For example: गृहम् आगच्छति
2. If the next word starts with a consonant, then म् should be pronounced and written as anusvara.
   For example: गृहं गच्छति

For difference between pronunciation of anusvara and म्, check this video.

णत्वम् - When न् changes to ण् in a word

There are many rules in grammar when न् changes to ण् in a single word. The simple rules to remember are:

1. When न् is immediately preceded by ऋ, र् or ष्
   For example: गुरुणा, चरणम्, विष्णुः, ऋषिणा
2. In a single word, between न् and ऋ, र् or ष्, when all the letters are vowels or क/ख/ग/घ/ङ/प/फ/ब/भ/म/य/व/ह/आङ्(उपसर्गः)/अनुस्वारः
   For example: रमणम्, नारायणः, परमाणुः, चषकेण
   Following this rule, the correct word is पर्णानि not पर्णाणि

Watch the video explaining the logic (reason) behind this णत्वम्