Letter
noun, の adjective
A hand paper is a letter because letters are generally written by hand on paper.
If you want a more graphic image, imagine writing a letter on your hand, and how much it would hurt to chop off your hand and send it.
The reading is double kun'yomi (body parts tend to make kanji in words change to a kun'yomi reading). Both kanji in this word had you learn that reading right from the start, though, so you should be able to read this word. Just watch out for the rendaku making it がみ, not かみ.
手紙が来る
the letter comes
手紙がある
there is a letter
手紙がとどく
the letter arrives
手紙をかく
to write a letter
手紙をもらう
to receive a letter
手紙を出す
to send a letter
母の手紙
mother's letter
先生の手紙
teacher's letter, doctor's letter
お礼の手紙
thank you letter
お手紙
letter
それは、父からの手紙です。
It is a letter from my father.
切手が足りなかったのか、学校からの手紙が中々来ません。
Perhaps, it didn't have enough stamps. A letter from the school still hasn't arrived.
外国への手紙の出し方を教えてくれませんか？
Can you teach me how to mail out a letter to a foreign country?