Spelling Tips: When to Change ‘Y’ to ‘I’

The spelling of words can be tricky when adding a suffix. For instance, there are some occasions when you need to change the final ‘-y’ to an ‘-i-‘ when modifying a word. We’ve compiled this handy guide to help you out!

Forming Plurals

The most common situation in which you’ll need to change the ‘y’ to an ‘i’ in a word is when forming plurals. In this case, it’s common to amend the ‘-y’ at the end of the word to ‘-ies’:

Baby → Babies

Lady → Ladies

Mystery → Mysteries

Third-Person Singular and Past-Tense Verbs

If a verb ends in a ‘y’ (such as ‘try’), you should change the ‘y’ to an ‘i’ when referring to someone or something in the third-person singular (i.e. ‘he’, ‘she’ or ‘it’). So while we say ‘I try’ in the first-person, we say ‘he tries’, ‘she tries’ or ‘it tries’ when using the third person:

Worry → Worries

Justify → Justifies

Hurry → Hurries

The same rule applies when conjugating the past tense of verbs, although in this case we add ‘-ied’. As such, the present tense ‘I try’ becomes ‘I tried’:

Worry → Worried

Justify → Justified

Hurry → Hurried

Comparatives, Superlatives and Adverbs

In the case of comparatives, we change the ‘-y’ to an ‘-ier’; with superlatives, we use ‘-iest’. The quality of being ‘more happy’, for example, is expressed with the comparative ‘happier’, while the ‘most happy’ person is the ‘happiest’.


Similarly, when forming an adverb from an adjective ending in a ‘y’, we change the ‘-y’ to an ‘-ily’. So, for example, the adjective ‘happy’ is modified to become ‘happily’.

Exceptions to the Rule

Unfortunately, the rule does not apply when modifying words in which a vowel precedes the ‘y’ (i.e. words ending in ‘-ay’, ‘-ey’, ‘-oy’ or ‘-uy’, since no English words end in ‘-iy’).

In these cases we simply pluralise as normal by adding an ‘-s’:

Boy → Boys

Trolley → Trolleys

Monkey → Monkeys

The third-person singular of a verb ending in ‘y’ is indicated by adding an ‘s’ (so ‘I enjoy’ becomes ‘he/she/it enjoys’) and the past tense of a verb ending in ‘y’ requires an ‘-ed’ (‘enjoyed’).

Exceptions to the Exceptions

There are plenty of exceptions to the rules above. The superlative and comparative of the adjective ‘sly’, for instance, can be spelled either ‘slyer’ and ‘slyest’ or ‘slier’ and ‘sliest’ (but the adverbial form can only be spelled ‘slyly’ not ‘slily’).

These exceptions make it tricky to eliminate mistakes without a lot of practice. One good option is to have a professional check your writing, since we will provide helpful feedback if we spot this kind of error in your work.

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