There are many perks to speaking the lingua franca of your time, but one of the downsides is that you’ll always doubt whether you’re using it right. English has almost as many variants as there are countries that use it as their official language. A great example of that is the past tense of the verb learn—is it learnt? Or is it learned?
Learnt and learned are both used as the past participle and past tense of the verb to learn.