I'm looking for an elvish translation for Heart's Mirror. I can find heart, but not mirror. Can anyone help?

Since mirrors don't exist in nature...good luck, try reflect or reflection

and you realize that Elven is only partially constructed--all three dialects.

there is a book of elvish and it's in the Apendix of The Lord of the Rings.

I began searching for answer to your question by conducting a Google search of several combinations and variations of the words “Elvish,” “translation,” and “mirror.” I finally found the following Quenya (High Elven) translation (http://www.elvish.org/elm/newwords.html):

ceniril(le) "mirror"; possible cognate of S cenedril (from Nen Cenedril "Lake Looking-glass"

The website states, however, that the words it lists “are not found (at least not exactly in such forms) in published corpus, but are commonly used by writers because of the lack of vocabulary. The words are based on other words, coined in agreement with Quenya, compounded or isolated.”

I decided to seek confirmation of the translation of the Quenya word “ceniril” by Googling the phrase “Quenya ceniril,” which brought me to several websites, including the following:

http://www.elfwood.com/~maija/Galadriel.3006428.ht...

This example website tells us that “I Ceniril Altarielwa” is the Elvish translation of “The Mirror of Galadriel.”

Many other websites can be found through this same simple Google search that confirm that “ceniril” is the accepted Quenya translation for “mirror.”

If you are interested in further self-exploration into Elvish, you might find the following website to be useful:

http://www.yourdictionary.com/dictionary-articles/...

It lists criteria for evaluation online English to Elvish dictionaries and recommends and provides descriptions of three specific dictionaries. (Of course a Google search of “Elvish translators” will provide you with dozens of other helpful online tools.)