NOTE:
When better is used as an adjective it is translated by meilleur or mieux depending on the context (see below, and note that meilleur is the comparative form of bon, mieux the comparative form of bien). The translation of the construction to be better than varies depending on whether bon or bien works originally with the noun collocate: their wine is better than our wine = leur vin est meilleur que le nôtre;
her new apartment is better than her old one = son nouvel appartement est mieux que l'ancien;
his new film is better than his last one = son nouveau film est mieux or meilleur que le précédent (both bon and bien work with the collocate in this last example). Other constructions may be translated as follows: this is a better bag/car = ce sac/cette voiture est mieux;
it is better to do = il vaut mieux faire or il est mieux de faire. As an adverb, better can almost always be translated by mieux. For more examples and particular usages, see the entry below.