Re: My favorite silent English letter is:

[PhilHibbs]

How is Hajj an English word? Marijuana would be better. Sure, it's a loan words from another language, but we added the 'j' for the English version of the word so it definitely counts!

[DrHyde]

How is hajj an English word? Same way that rendezvous and skiff and alcohol are.

[PhilHibbs]

I think most people would make a distinction between words that have been adopted into mainstream English usage, and foreign language words that we use because there isn't an English word. Hajj isn't a generic word that can be used for any other purpose. It has a specific meaning, and it is inappropriate - even offensive - to use it in any other context. I would never "go on a hajj to Bletchley Park", for instance, but I would "go on a pilgrimage" to it. So while technically it is "a word that is used in the English language", it's very much a borderline case. Although it's legal in Scrabble, so maybe I'm wrong.