The word "did" can have many substitutes depending on the context of the sentence. Some common synonyms for "did" include "completed", "accomplished", "performed", "executed", "achieved", "made", "carried out", "carried through", "fulfilled", "acted", "worked", "undertook", "implemented", "fulfilled" and "carried off". These words can be used to convey a sense of action that has been done in the past. For example, instead of saying "I did my homework," you could say "I completed my homework," or "I fulfilled my homework." Using synonyms can help to add variety to your writing and make it more engaging for the reader.