“Lightening” and “lightning” are only different by one letter, but their meanings are far from the same.
Lightening – “to lighten” something, whether you’re talking color or weight. You can often use “lighten” in its place as well.
Example: The designer is lightening the background of our logo because it is too dark. We brought in a contractor to lighten our workload.
Lightning – the streaks or bolts of light from the sky during a thunderstorm.
Example: The lightning hit the transformer outside our office, causing us to lose electricity.
When trying to choose the right one to fit your meaning, take off the endings. You then have the root words “lighten” and “light”, which makes it easier to tell which one to use (do I lighten the load or flash light in the sky?). It sometimes helps to over-pronounce “en” in “lighten” to really make you stop and think if it’s the right choice.
I hope these tidbits help in lightening your load of word choice errors so lightning errors don’t strike twice.