椅子下面怎么说用英语写

"Under the chair" or "beneath the chair" are both ways to describe the area beneath a chair in English. Here are a few examples of how you might use these phrases in a sentence:
I dropped my pen under the chair and had to crawl around to retrieve it.
The cat was hiding beneath the chair, waiting for me to walk by so it could pounce.
I noticed that there was a small puddle of water under the chair, and realized that I had spilled my drink earlier.