The base or main part that something is built on.
The house's fundament is its foundation.
這棟房子的基礎就是它的地基。
The main idea or principle that something is based on.
The fundament of her argument was solid evidence.
她論點的基礎是確鑿的證據。
The buttocks.
He fell on his fundament.
他摔倒在他的屁股上。