* Silent letter: This is the most common and straightforward term, though it doesn't explain the underlying linguistic phenomenon.
* Ethymological letter: This emphasizes the letter's historical significance, reflecting how the word was pronounced in an earlier stage of the language.
* Historical letter: This is similar to "etymological letter" but emphasizes the letter's role in showing the word's origins.
* Non-phonetic letter: This emphasizes that the letter doesn't represent a sound in the current pronunciation of the word.
* Graphem: This term refers to a written symbol that represents a sound or a combination of sounds. This is more technical and less commonly used in everyday language.
Ultimately, the best term depends on the specific context and the aspect of the letter you want to highlight.