Tree, Wood
noun
The kanji and the word are exactly the same. That means they share meanings as well.
き
Since this word is made up of a single kanji, it should use the kun'yomi reading. When learning the kanji, you didn't learn that reading, so here's a mnemonic to help you with this word: You walk up to the tree. You have to get inside, because it takes you someplace secret. So, you take out your key (き) and put it in the slot, opening the door in the tree so you can slip inside.
これはサクラの木ですか？
Is this a cherry tree?
このテーブルは木で、できてます。
This table is made of wood.
あの木の上にツリーハウスをつくりたい。
I want to build a tree house on that tree over there.