Explanation
Express that something is not impossible, meaning it is possible or could be done.
Formation
Verb-ないform + ことはない
Detailed explanation
The ～ないことはない grammar point is used to express a double negative, meaning that something is not impossible, implying that it is possible or could be done. Essentially, it downplays the possibility or ability to do something but still acknowledges that it's possible.
Examples
Kare ga konai koto wa nai.
It's not that he won't come (it's possible that he will come).
Ano mondai ga tokenai koto wa nai.
It's not impossible to solve that problem (it can be solved).
Sono shigoto ga muzukashikunai koto wa nai.
That job is not without difficulty (it has some difficulties).
Kanojo ga tadashikunai koto wa nai.
It's not impossible that she is right (she could be right).
Practice
Grammar content sourced from hanabira.org.