The word tyelpetéma in tengwar of the Quenya mode.2 The first character, equivalent to 'tyë', is a palatal of the tyelpetéma series.
One of the témar or sound-series of the tengwar as used to represent the sounds of the Quenya language.
The tyelpetéma appears to have been unique; while each of the other four series consisted of a set of six individual 'letters', the palatal sounds of the tyelpetéma were formed by adding a mark of two dots beneath another character, as in the example above.3 This is the equivalent of adding a 'y' after the letter in English to form a single distinct consonant sound. To use Tolkien's own example from Appendix E to The Lord of the Rings, the sound 'ty' here has the same sound as the initial consonant in the (British) pronunciation of the English word 'tune' - something close to, but distinct from, 'ch'.
Notes
1
The choice of the Quenya word for 'silver', tyelpë, is for purely phonetic reasons: it happens to start with a palatal sound, 'ty', that belongs to this series.
2
Replicating a specific 'mode' of tengwar is extremely difficult, and this transcription is necessarily approximate. The difficulties are particularly acute in this case because examples of 'true' Quenya are extremely rare: most of Tolkien's transcriptions to tengwar are from Sindarin, English or, in the unique case of the Ring inscription, the Black Speech.
3
In fact Tolkien tells us that this was the 'usual' method of marking a palatised sound, not the only means of doing so. We are given no hint, though, as to what other methods may have been used. (The Lord of the Rings, Appendix E (i), The Fëanorian Letters).