Is repeating a word OK?
Simple answer: Yes, if it’s a common word; no, if it’s an uncommon word.
If you’re writing an essay about your dog, you’re going to need to repeat your dog’s name, or the word dog, or both, many times before you’re through. There just aren’t many useful synonyms for dog. Canine companion? Animal that makes woofing noises?
Just stick to dog.
Are you doubting me? Are you afraid that repeating dog, dog, dog will make you sound trite? OK, let’s try an experiment. Get out today’s newspaper, scan the front page, and count how many times you find the word said. Guess what? Every quotation includes said. It’s repeated over and over. Newspapers never use synonyms for said (such as reply, state, remark, note). It’s said, said, said, said.
You never noticed before, did you? It’s true. Our brains skip over ordinary words (said, the, and, house, money, store and many more), never noticing how often they’re repeated.
The prohibition against repeating a word applies only to conspicuous words. You can say that your trip to the Magic Kingdom at Walt Disney World was wonderful exactly once. After that, you need to find some different words. It was fun, hilarious, pleasurable, fascinating, and so on.
Better yet, be specific about what you did and how you felt. You laughed at the funny tombstones behind the Haunted Mansion. You slurped a milkshake on Main Street. You chatted with Mary Poppins and got her autograph. You applauded when Goofy skipped down the street during the parade.
Yes, it was wonderful! (But only once, right?)