There are some rules in English pronunciation, but there are a ton of exceptions and inconsistencies. To give you an example of a reliable rule: when a plural word ends in a vowel or a voiced consonant, the "s" is pronounced as "z" (eyes, dogs), but when it ends in an unvoiced consonant, it's pronounced as "s" (cats). Our BoldVoice, we like to teach these rules because they are quick wins for most people. Then, a lot of the hard work comes in practicing and memorizing the many, many exceptions.