Lightening and lightning look similar, but they have different meanings and pronunciations.
Lightening is a form of the verb lighten. Use it for an action or process that makes something lighter. The change may involve color, weight, mood, work, or severity.
- The morning sun is lightening the sky.
- Sharing the boxes is lightening her load.
- His joke was helpful in lightening the mood.
Lightning is the bright electrical flash that occurs in the atmosphere, usually during a storm. It is a noun, although it can also describe something connected with that flash, as in lightning strike.
- A bolt of lightning struck the tree.
- We went indoors when we saw lightning.
Context usually makes the choice clear. If a sentence describes something becoming less dark, less heavy, less serious, or more cheerful, use lightening. If it refers to stormy weather or an electrical flash in the sky, use lightning.
Compare these sentences: “The clouds are lightening” means the clouds are becoming brighter or less dark. “There is lightning in the clouds” means electrical flashes are visible. Checking the intended meaning will help you choose the correct spelling.