"يتدرّب كل يوم."

You knew we are going to answer you, that's great! I am glad to see that the relationship between the learners and the contributors is stronger than ever.

To answer your question, however, I would say that ‘each’ and ‘every’ are two almost identical words, especially in that each (you cannot say ‘every’ here ^_*) places emphasis on a different aspect of the sentence.

• ‘Each’ means ‘one by one separately’ and emphasizes individuality. (in a way similar to every single.)

• ‘Every’ means ‘all of them in total’ and emphasizes the sum, total and the wholeness. It is half the way between ‘each’ complete individuality and ‘all’ complete wholeness.

However, native speakers barely pay attention to this subtle difference in sense. Thus, the real difference is limited to grammatical aspects, and here are some insights:

• ‘Each’ is used when there are two objects; here, ‘every’ is not used.

There were two of them. They each were handsome.

• ‘Each’ can be used as a pronoun, but ‘every’ cannot.

We awaited the analysis results. Each was terribly nervous.

• With adverbs (practically, nearly, almost, etc), only ‘every’ is used.

She knows almost every technique needed to pass the exam.

• ‘Every’ is used to refer to repeated, regular events.

Which applies to the example above; it is preferred to say ‘I train every day’ rather than ‘I train each day,’ unless you're emphasizing the individuality of these days.

I hope this has helped you. All of luck!

P.S. My name is Mohamed, and not ‘Chamad.’ :)

مع ال adverbs of frequency مثل every day, weekly, always, sometimes نستخدم المضارع البسيط. :)