Are Vardo and Varda two different people?

As the fellowship was parting from Lorien, Lady Galadriel sings a song in Elven. The song talks about Elbereth.

The poem goes like this:

Ai! laurië lantar lassi súrinen,

yéni únótimë ve rámar aldaron!

Yéni ve lintë yuldar avánier

mi oromardi lisse-miruvóreva

Andúnë pella, Vardo tellumar

nu luini yassen tintilar i eleni

ómaryo airetári-lírinen.

Sí man i yulma nin enquantuva?

An sí Tintallë Varda Oiolossëo

ve fanyar máryat Elentári ortanë,

ar ilyë tier undulávë lumbulë;

ar sindanóriello caita mornië

i falmalinnar imbë met, ar hísië

untúpa Calaciryo míri oialë.

Sí vanwa ná, Rómello vanwa, Valimar!

As you can see there is a Vardo and a Varda. When Frodo translated it he only spoke of Varda. Is it a typing mistake or are Vardo and Varda two different people? Or maybe it's some Elven grammatical rule?