A snow crystal is a single crystal of ice, whereas a snowflake is a more general term that can mean an individual snow crystal, or an aggregation of snow crystals colliding together as they fall from the sky.
A snow crystal is formed in the sky when water vapor converts to ice. (This process is called deposition, as it does not go through the liquid phase.)
When we see them on the ground, we see their intricate patterns. Each snow crystal is different because each experiences different conditions as they fall from the sky - different paths, different temperatures, different humidity - all of which affect how they grow and develop. Because of this, every snow crystal really is unique.
If you're intrigued by the beauty and science of snow crystals, have a look at these resources:
- Kenneth G. Libbrecht, professor of physics at the California Institute of Technology (Caltech)
- The official website of Wilson A. Bentley, operated by the Jericho Historical Society
- The Bentley Snow Crystal Collection of the Buffalo Museum of Science
