marný in English:

a futile attempt/effort; it is futile to do something

I did my best to learn to dance but all my attempts proved futile.

Going to the local police for help is often futile

But so far as I can see, thinking about such things is not futile.

It's completely futile trying to reason with him - he just won't listen.

It just seems so futile, you know? All these women and nothing!

Although stoichiometrically possible, these modes involve futile cycling of carbon across the internal membranes to dissipate energy

No sooner had I Fixed the washmashine than it turned out that my effort was futile

... later years on a futile search for a unified...

Such a fight would be both futile and ridiculous.

It isn't futile to go to university.

If one plants an oak, it is futile to hope to soon be able to take cover under its leaves.

Fashion-conscious people are usually vain and selfish.

in vain

But, knowing precisely sadness and love and death, and that they are vain images when we observe them from the calm space where we should shut ourselves in, he kept on weeping, and desiring love, and fearing death.

I think John is quite selfish, and a little bit vain. He isn't easy to get on with.

Favour is deceitful, and beauty is vain: but a woman that feareth the LORD, she shall be praised.

His vain efforts to seduce her showed he was barking up the wrong tree; she was a mother of two tots.

Give up, give up your vain pursuit!

How vain it is to sit down to write when you have not stood up to live.

A person may be proud without being vain. Pride relates more to our opinion of ourselves, vanity to what we would have others think of us.

We have worked hard and I would like to think that our work will not be in vain.

I think you’d have to be really vain to spend ages in a photo booth.

this vainglorious boast of personal infallibility

Dennis is very concerned about his appearance. He spends long hours shopping, trying clothes on and choosing shoes. He visits a beautician regulary and has installed huge mirrors in each room of his house. He's vain.

She was young handsome vain and giddy and completely the slave of fashion.

The finest words in the world are only vain sounds, if you cannot comprehend them.