1. For new users from v3.6.4 and later, the same word can be cached respectively from Cambridge and Merriam Webster dictionaries.
2. For old users from v3.6.3 and prior, since sqlite doesn't support table schema modification, looking up the same word from a different dictionary will update the previous cache record (if present) with the current search result. Or, if the previous cache of words doesn't mean too much to you, you can `rm -rf $HOME/.cache/cambridge` and have a clean slate with 1 feature.