This is the 343rd most frequent Chinese word.
只能
"Can only" or "can merely."
只能 is used here to indicate a limitation in options or actions due to circumstances.
我现在很忙，只能等我有空时再帮你。
I am very busy right now; I can only help you when I have time.
只能 suggests an inevitable course of action following an unforeseen issue.
他发现问题后，只能结束实验重新开始。
After he discovered the problem, he could only end the experiment and start over.
只能 specifies the lack of alternatives, focusing on the sole available option.