hard

What body part is pronounced as one letter but written with three, only two different letters are used?
Common Wrong Answers
“I”
Although 'I' is pronounced like the letter, it is not a body part.
“Arm”
While 'arm' is a body part, it does not match the criteria of being pronounced as one letter and written with three letters.
“Toe”
Toe is a body part but does not fit the riddle's description of having three letters with only two different letters.
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hard
Pronounced as one letter, And written with three, Two letters there are, And two only in me. I'm double, I'm single, I'm black, blue, and gray, I'm read...
easy
I have an eye but am blind, a sea, but no water; a bee, but no honey; Tea but no coffee; and a why, but no answer. What am I?
easy
What word has 5 letters but is pronounced like only one letter?
medium
Name 10 Body Parts with 3 letters each (no profane words).