* Across, through, or between: This is the most common meaning of "dia-". For example:
* Diameter: The distance across a circle through its center.
* Diagonal: A line segment that connects two non-adjacent vertices of a polygon.
* Diaphragm: A muscular sheet that separates the chest cavity from the abdominal cavity.
* Completely, totally, or thoroughly: This meaning is less common, but still valid. For example:
* Diabolical: Extremely evil or wicked.
* Diagnosis: The identification of the nature of a disease or disorder.
* Double, twofold, or twice: This meaning is more specific to certain words. For example:
* Diatomic: A molecule composed of two atoms.
* Dichotomy: A division into two parts.
The specific meaning of "dia-" will depend on the word in which it is used. If you are unsure of the meaning, it is always best to consult a dictionary.