"Straight" can be translated to "笔直" in Chinese.
It comes from the word "straight" which means "直的" or "直线的" in Chinese.
Example:
"Keep your back straight." (保持你的背部笔直。)
"The road ahead is straight." (前面的道路是笔直的。)
"He has a straight nose." (他有一个笔直的鼻子。)