almost unnoticeable 几乎察觉不到
an unnoticeable difference 细微的差别
unnoticeable change 微小的变化
virtually unnoticeable 几乎看不见
A: Did you notice any change in her behavior?
A：你发现她的行为有什么变化吗？
B: Not really, the changes were almost unnoticeable.
B：没有，那些变化几乎难以察觉。
1) 不显眼的
2) 细微的
3) 难以察觉的
1. 不显眼的，难以察觉的
adjective
1. Not easily seen or heard; inconspicuous.
Synonym: inconspicuous, imperceptible, subtle