Spellings of ĐevaNāgarī (देवनागरी)
Correct Spellings: DevaNagari (ĐevaNāgarī) & DevNagari.
Incorrect Spellings: Devnagri, Deonagari, Devnagiri...
Some people argue that 'Devnagari' is incorrect spelling! It is not.
I thought of the following reasons!
'व' (v) is not a pure consonant but a semi-vowel! Its pronunciation is in between vowel 'उ' (u) and vowel 'अ' (a). So adding a vowel 'अ' (represented by 'a') is not desperately required after 'v'. Also, in Indian languages there is a phenomenon called 'schwa deletion' (अ-मात्रा लोप).
Moreover how a spelling (Devnagari, i.e.) which is used by a lot of people can be called incorrect.
But scholars prefer the spelling - 'Devanagari'.
If you ask me which spelling should be preferred, whether 'Devnagari' or 'Devanagari'; my answer will be 'ĐevaNāgarī'. I write 'ĐevaNāgarī' instead of 'Đevanāgari' to emphasize that 'Nāgarī' is the important part of the word!
We should use 'Nāgarī' instead of 'ĐevaNāgarī' when we refer it many times, i.e. as a short form.
Alternate Transliterated Spellings
'Devanaagaree' is a better spelling as per commonly followed rules of transliteration. As per our _naagaree-128 scheme, you will write '_devanaagaree' as 'D' stands for 'ड', 'd' for 'द'. ĐevaNāgarī is the spelling as per our another (newer) transliteration scheme called 'Nīrajā-Latin'.