Tentative language is a very important feature of academic writing which overseas students often find difficult. Tentative means cautious, or careful. Let me give you an example of language which is NOT tentative:
The Queen of England is very popular and is loved and respected by her subjects.
This sentence is too factual. It sounds like every single of her subjects loves and respects her. Probably there are some people who don’t love and respect her and she might not be popular with everyone. A better sentence would be one using tentative language, for example:
The Queen of England appears to be very popular and seems to be loved and respected by many of her subjects.
This is much better academic style. You are being cautious, you are ‘hedging’.
Of course now I have to show you a link which gives you examples of hedging language and an exercise. Here’s the link to Andy Gillett’s exercise at his fantastic site at the University of Hertfordshire. Choose the HEDGING link at the top of the page you come to. Read his introduction to hedging , his language examples and do the exercise at the bottom. Finally, make sure you try to use this feature in your writing.