应该没有任何关联的两个单词吧.
less是little的比较级 既可以做形容词也可以做副词 意思是“较少的”或“更少”
比如:
The company has less money and fewer staff than last year.
Let's speak less and listen more.
unless是连词,意思是“除非”,可以用not...if来替换 比如:
You will fail unless you work hard.(除非你努力工作,不然你会失败的)
=You won't fail if you work hard.
总之这两个单词除了拼写类似,应该没什么关系.