Like Iansinclair said.
These expressions were not created in the same way as science and engineering terms have been put together. Musicians in different places in Europe over different time periods searched for words to describe their vision for their compositions that went beyond just the notes. In different time periods, or among different composers, some words even had slightly different meanings.
For interpreting this piece that you're preparing for an exam, I imagine your teacher is also guiding you and you should feel free to ask that question. For interpreting "rallentando" also get into the piece yourself. Try to understand it as feeling and phrasing. If rall. or rit. are written in, what is happening musically? Is it coming to a gentle end, fading away into the sunset? Was there a dramatic climax in a surge of emotion, and now it is sighing in relief with all that intensity falling away? What is going on in your music, as music?