Science is two things. Describe what those two things are.
There are many more than two things that can describe science. If you look 'science' up in the Oxford dictionary, for example, words like 'systematic', 'observation', and 'experimentation' are things that could be used to describe science. However, I suspect your tutor is looking for two specific things that he or she has taught you. Without knowing your syllabus I have no idea which particular two things they are looking for you to say. In this case I doubt there is any substitute for reading their course material.
Science is you and nature. Science is how you describe nature.
If I had to choose two words, I would choose testable and repeatable. Testable because you have to make claims and then test them. Repeatable because if you do something, someone else should be able to confirm your results by doing what you say.
I would say that Science is knowledge gained through observation & experimentation. However, as mentioned above, it looks like you are looking for a specific phrasing of the definition, and you may want to refer to your course materials.
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