Final answer:
The subject is English, and it covers the rules for pluralization of nouns ending in -o preceded by a vowel, the deletion of the silent 'e' when suffixes are added, the addition of the feminine suffix -ess, and the spelling of the [s] sound in English words.
Step-by-step explanation:
The student's question pertains to the formation of plural nouns in English. Specifically, if a noun ends with an -o preceded by a vowel (a, e, i, o, u), the rule of thumb is to add an 's' to form the plural. Examples of such words include 'ratio,' which becomes 'ratios,' and 'studio,' which becomes 'studios.' This rule contrasts with other pluralization rules where sometimes 'es' is added, or changes are made to the word's ending.
Regarding final silent 'e,' if a word ends in a silent 'e' that indicates the previous vowel sound is long, this 'e' is often deleted when adding a suffix starting with a vowel. An example is 'race' becoming 'racing,' where the final 'e' is dropped before adding '-ing.'
Additionally, when forming feminine counterparts of masculine nouns with the suffix -ess, such as 'waitress' from 'waiter,' or 'actress' from 'actor,' an unusual deletion occurs. The final 'e' or 'o' before 'r' in the masculine noun is often dropped when adding the -ess suffix.
Spelling the [s] sound at the end of words can be done with , , or . However, few free base words end with an [s] sound spelled with a single without an insulating final 'e,' except for some common words like 'bus' and 'gas.'