Is it w or wn?I have no idea,kindly help me out? What about in words like rogue,does ue or u count as silent consonants although they are clearly vowels?
Technically speaking, there are no "silent letters" in English words. That's because our letters do not represent pronunciations the way you think they do.
Specifically, there are no “silent” letters in dawn /dɔn/ or lawn /lɔn/: the ‹aw› digraph represents the phoneme /ɔ/ there, just as it does in law. After all, lawn is pronounced just like law with an extra /n/.
We call this /ɔ/ phoneme the THOUGHT vowel, and it like all sounds in English has many, many, many possible spellings, and ‹ough› is one of those.
There are no silent letters in thought either, just a digraph followed by a tetragraph followed at long last by a monograph to create /θɔt/.
A better question would be to ask about gone /gɔn/, since that one cannot be explained by the LOT–CLOTH split, in that it does not have a voiceless fricative after it like off, moth, and boss all do.
But that you didn’t ask. :)
In the case of rogue, /rog/, the ‹gue› at the end is a trigraph that here represents the phoneme /g/. Other examples include analogue, dialogue, epilogue, fatigue, intrigue, league, plague, vague.
As with all mappings between graphemic sequences and phonemic sequences in English, which are inherently many-to-many, there are many other words where that same graphemic sequence produces a different set of phonemes, let alone phones. Examples where ‹gue› is not a trigraph and does not represent /g/ include tongue, argue, ague, segue.
As soon as you start talking about “silent letters” in English, you’ve given tacit approval to a model that doesn’t apply to English, so it’s difficult to provide a “correct” answer to a question that is inherently misleading.
I again request that you please read this.