No, it is not. The word letter can be a noun for a symbol (alphabet) or correspondence (mail). It can be a verb mean to enscribe.
Rapidly.
The adverb of meaningful is meaningfully.An example sentence is: "he meaningfully wrote her a letter".
newly, nobly
ably
No, it's an article adjective!
that's a noun
there
T is not an adverb, it's a letter in the English alphabet. Tenderly, truthfully, triumphantly, and typically are a few adverbs that begin with the letter T.
· ably · also · anew · away
een or oer
ly
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