If you mean the hypothesis in the experiment, then the hypothesis is the forecasting of the results of it. Let me give you an example. If you are making the research on how many flowers are in the bush of roses, your hypothesis will be the following, each branch will be covered with five roses.
But if you need the hypothesis in the field of statistics, it is more complicated.
In statistics, a hypothesis is a proposition that is consistent with known data, but has been neither verified nor shown to be false.
Statistical hypothesis refers to a statement on which hypothesis testing will be based. Particularly important statistical hypotheses include the null hypothesis and alternative hypothesis.
The hypothesis is something that you predict will happen. This term is commonly used while experiments or reports. Firstly you state the hypothesis and then, make an experiment. Try to guess the outcome.
I hope my explanation was helpful.
As for me, when I need to define some terms, I would likely to use the dictionary. However, I am a hundred percent sure that the definition is in your textbook.
If not, you can just google it.
The hypothesis is the starting point of your future experiment and is made according to the evidence.
The hypothesis is simply testing the phenomenon to investigate whether it is right or wrong.