To do something in vain means that you do not succeed in doing what you are trying to do; to try in vain is to fail.
An attempt to do something that failed
It means do not dwell on the past as if you could have changed something to make it work.
This means that your are working in vain. That something does not worth the effort of working on because it will not be profitable.
To do something in vain means to do it without success or without achieving the desired result. It implies that the effort put into the action was wasted because the outcome was not favorable or did not meet the intended goal.
in vain means the expected result is not going to happen
I think you mean "vain".
for no point
To die in vain means that you died for a cause but your death did not change anything.
Vain means conceited, or it may mean to no avail. Here are some sentences.She tried in vain to stand on her head.He was as vain as a peacock."You're so vain!" (a song by Carly Simon)
Without effect or to no purpose
Conceited means having an excessively favorable opinion of one's abilities, appearance, or accomplishments. It implies being vain or excessively proud.
Vain