Hi there. I realise that this seems to be getting repetitive, but yes - once again - this is an issue of comparative formality. As a rule, if you have two options like this, where one is a single Latin-style word, and the other is a multi-word phrase, you can be fairly sure that the first will be the more formal term. As Marija says above, in conversation you would say 'Make sure you turn off the lights', because 'ensure' would be sound unnatural in this situation. However, in written instructions about the same topic, it would be quite appropriate to use the word 'ensure'. You'll find that this rule works almost every time. Use the single Latin words for your essays, and the multi-word expressions (usually Germanic roots) for conversation and more informal contexts. The English language is like a mixed-race child, ever conscious of its dual parentage.

They have the same meaning, you can use the interchangeably. I can make sure that you get the letter. I can ensure that you get the letter. However in some sentences they require a bit different syntax. To ensure the success of the movie you have to do something original. To make sure that the move is a success you have to do something original. Also, sometimes they are used in different contexts. You would say "Make sure you turn off the lights", you wouldn't say "ensure you turn off the lights" Hope that helps :)

They have essentially the same meaning. "I will make sure that the letter is delivered." "I will ensure that the letter is delivered."