If you look up an informal word in a monolingual dictionary, you will often find a neutral equivalent as part of the definition or explanation. For example, the Cambridge Advanced Learner’s Dictionary of English entry for kid says: ‘informal: a child or young person’. Use a dictionary to find neutral or more formal words for these:

1. kip  sleep
2. a pal 
3. a mate 
4. swot 
5. ta! 
6. brainy 
7. gross 
8. dodgy