Dilation (noun)

1. The action or process of making something larger or wider.
2. The state of being expanded or dilated, especially of a blood vessel or pupil of the eye.

Origin:

Late middle english: from latin dilatatio(n-), from dilatare "to spread out".

Examples:

1. The dilation of the pupils is a sign of excitement.
2. The doctor recommended dilation of the artery to improve blood flow.
3. The dilation of the vagina during childbirth helps the baby to pass through.
4. The dilation of the galaxy is a result of its expansion over time.
5. The dilation of the pupil allows more light to enter the eye, improving vision.