Thunderstruck

We had quite a spectacular thunderstorm in Toronto the other day, with lashing rain and lots of those flashes of light that come with a big boom.

Yes, LIGHTNING. 

Notice the spelling. The noun is not "lightening". Lightening is something you do to your hair. They were originally the same word, but the noun for the electrical storm sense has had this special spelling since it first showed up in the language in the 14th century, just in case someone reading "a huge bolt of lightening" might get confused and think it meant a large amount of peroxide. 

Apparently the earlier, Old English word for the phenomenon had been "leye-rash" (literally, light move fast). 

Just to be somewhat confusing, not to mention annoying (otherwise we would be talking about some logical language rather than English) there is a verb "to lighten" meaning "(of lightning) flash", as in "It rained, thundered, and lightened all night". If you put this in the progressive tense it would be "It was raining, thundering, and lightening".

Summary: LIGHTNING is the noun, LIGHTENING is the verb.

Photo by Brandon Morgan on Unsplash