vain
(without success; useless)
- They worked day and night in a vain attempt to finish the job on time.
- We tried in vain to persuade him to come with us.
(too proud of your appearance, abilities or achievements in a way that annoys other people)
- He was always too vain of his abilities.
- She is very vain about her dress.
vein
(any of the tubes in your body that carry blood to your heart)
- The nurse is trying to find a vein in his arm.
- The veins carry blood to the heart from the other parts of the body.