Final answer:
To form the plural of a singular word ending in -ax, change 'ax' to 'aces', resulting in words like 'taxes' and 'faxes.' The suffix -ess is added to make nouns feminine, but its usage is decreasing over time.
Step-by-step explanation:
When the singular form of a word ends in -ax, the rule to form the plural is to change the 'ax' to 'aces.' An example would be the singular noun 'tax,' which becomes 'taxes' in its plural form. Similarly, 'fax' turns into 'faxes' when pluralized. This rule does not apply to all words ending in -s, as some, like 'news' and 'physics,' are treated as singular despite their plural appearance in form. In contrast, the addition of the suffix -ess to a noun typically indicates a feminine version of that word, as in 'hostess' from 'host.' However, usage of -ess is declining due to changing social attitudes on gendered language.