These three are not synonyms, and confusing them is one of the fastest ways to lose ground in a judging interview.
Question — what you want to know. Does soil pH affect radish growth?
Hypothesis — a proposed explanation with a mechanism. Radish growth declines in acidic soil because low pH reduces the availability of phosphorus to the roots.
Prediction — what you will observe if the hypothesis is right. Plants in pH 5.0 soil will have lower dry mass at 28 days than plants in pH 6.5 soil.
The hypothesis is the part students most often skip: they write a prediction and call it a hypothesis. The giveaway is the absence of the word "because". A hypothesis without a mechanism cannot really be wrong for an interesting reason, and it gives a judge nothing to ask about.
Write all three down separately before you start. If your prediction does not follow from your hypothesis, something in your reasoning needs work.