A student wants to make the plural of 'book.' She knows many plurals end in -es, so she writes 'bookes.' What error has she made?
ANo error — 'bookes' is acceptable in informal writing
BShe added -es only to words ending in a vowel — book ends in a consonant so -s is correct
CShe over-applied the -es rule; -es is only for sibilant endings (-s, -ss, -x, -z, -ch, -sh), not all consonants
DShe should have doubled the final k before adding -es
The -es ending is for sibilant sounds specifically: -s, -ss, -x, -z, -ch, -sh. The reason is phonological — these sounds crash together when you try to add -s directly (try saying 'boxs' or 'dishs'). 'Book' ends in a plain consonant that doesn't cause this problem, so the correct plural is simply 'books.' Knowing the rule means knowing its specific trigger condition, not just that -es plurals exist.
Question 2 Multiple Choice
Which pair correctly applies the rules for nouns ending in -y?
Ababy → babys, boy → boyes
Bbaby → babies, boy → boys
Cbaby → babyes, boy → boies
Dbaby → babies, boy → boies
The -y rule depends on the letter BEFORE the y. 'Baby' ends in consonant + y (b-y), so y changes to i and you add -es: babies. 'Boy' ends in vowel + y (o-y), so you just add -s: boys. The key habit is always to look one letter back from the y before deciding which rule to apply.
Question 3 True / False
The noun 'dish' forms its plural as 'dishes' because -sh is a sibilant ending that requires adding -es.
TTrue
FFalse
Answer: True
Correct. 'Dish' ends in -sh, which is on the list of sibilant endings: -s, -ss, -x, -z, -ch, -sh. These endings already make a hissing or buzzing sound, and adding a plain -s directly would create an unpronounceable cluster ('dishs'). Adding -es inserts a vowel sound that separates the two sibilants and makes the plural pronounceable: dish-es.
Question 4 True / False
The plural of 'monkey' is 'monkies' because 'monkey' ends in -y.
TTrue
FFalse
Answer: False
The y→ies change only applies when a CONSONANT comes before the y. 'Monkey' ends in e-y — a vowel (e) comes before the y. When a vowel precedes the y, you simply add -s: monkeys. Many students apply the y→ies rule to all words ending in y without checking what comes before it — this is the most common error with this pattern.
Question 5 Short Answer
A noun ends in the letter -y. What is the correct process for forming its plural, and why does it matter what letter comes before the y?
Think about your answer, then reveal below.
Model answer: Check the letter immediately before the y. If it's a consonant (baby, city), change the y to i and add -es (babies, cities). If it's a vowel (boy, day, key), just add -s (boys, days, keys). The letter before y matters because it determines the sound: consonant + y shifts in pronunciation and spelling when a suffix is added, while vowel + y is already smooth and needs no change.
The practical habit is simple: look one letter back, then decide. This three-step check — sibilant ending? → -es; -y ending? → check what's before it; otherwise → -s — handles the regular plural pattern for nearly any noun.