The Rule in One Sentence
When you turn an adjective into an adverb by adding -LY, and the adjective already ends in consonant + Y, the Y changes to I and you add LY. The resulting ending -ILY is pronounced /əli/ or /ɪli/ in two unstressed syllables.
So happy becomes happily /ˈhæpəli/, busy becomes busily /ˈbɪzəli/, angry becomes angrily /ˈæŋɡrəli/. The old ending /i/ of the adjective expands into /əli/ for the adverb.
The Spelling Rule You Cannot Skip
The Y-to-I change is the spelling foundation. Without it, you would write *happyly or *busyly, which English does not allow because of the 'no I + I as neighbours' rule. The flow is:
- Take the adjective: happy, lucky, angry, busy, easy.
- Drop the Y: happ-, luck-, angr-, bus-, eas-.
- Add -ILY: happily, luckily, angrily, busily, easily.
How to Say It
The Common Adverbs
This rule generates many of the most useful adverbs in English. Master the pattern once, and the rest follow.
- happy → happily /ˈhæpəli/
- lucky → luckily /ˈlʌkəli/
- busy → busily /ˈbɪzəli/
- angry → angrily /ˈæŋɡrəli/
- easy → easily /ˈiːzəli/
- noisy → noisily /ˈnɔɪzəli/
- steady → steadily /ˈstedəli/
- hungry → hungrily /ˈhʌŋɡrəli/
- heavy → heavily /ˈhevəli/
- merry → merrily /ˈmerəli/
- silly → sillily (rare; usually 'in a silly way')
- tidy → tidily /ˈtaɪdəli/
Watch Out: -LY After a Vowel + Y
The Y-to-I change only applies after a consonant. Adjectives ending in vowel + Y keep the Y unchanged when adding -LY. The result is /li/ in one syllable rather than /əli/ in two.
- gay → gaily /ˈɡeɪli/ (note: actually a Y-to-I change, but only because of an old spelling rule)
- coy → coyly /ˈkɔɪli/ (Y kept, simply add LY)
- dry → dryly or drily (both spellings used)
- shy → shyly /ˈʃaɪli/
- sly → slyly /ˈslaɪli/
The 'Daily / Yearly / Hourly' Subgroup
Some adverbs end in -LY but are not formed from adjective + -LY in the regular way. They come from time-noun + -LY, and they are also adjectives.
- daily /ˈdeɪli/ — once a day; can be both adjective and adverb
- weekly /ˈwiːkli/
- monthly /ˈmʌnθli/
- yearly /ˈjɪərli/
- hourly /ˈaʊərli/
These are pronounced as a single fast /li/, not /əli/, because they have only two syllables and the I is the stressed vowel of the first syllable, not a connector.
The Two Big Exceptions
1. Adjectives that already end in -LY
If an adjective ends in -LY (like friendly, lovely, silly), you cannot add another -LY to make an adverb. You have to use a phrase: in a friendly way, in a lovely manner, in a silly way. English does not allow the awkward friendlily in normal use.
2. -ICALLY adverbs lose the -AL syllable
Adverbs from -IC adjectives gain -ALLY in writing but drop the -AL- in speech. Basically is /ˈbeɪsɪkli/ (3 syllables, not 4). Specifically is /spəˈsɪfɪkli/. The famous exception is publicly, which has no -ALLY at all in either spelling or speech.
Why /əli/ Rather Than /ɪli/
You will sometimes see -ILY transcribed as /ɪli/ instead of /əli/. Both are accurate, depending on speaker and speed. In careful speech, the I is a near-/ɪ/. In quick or American speech, it usually becomes a clear schwa /ə/. Either way, the syllable is short and unstressed; the stress stays on the original adjective syllable.
Practice Drill
Read these aloud, focusing on the unstressed -ILY ending: happily, easily, busily, angrily, heavily, hungrily, noisily, steadily, luckily, merrily. The two final syllables should sound light and quick. Don't put stress on the I.
Once you know this rule, you can confidently form and pronounce dozens of common adverbs from familiar adjectives, and you will avoid the very common error of writing *happyly or pronouncing the -ILY as a stressed /ɪlaɪ/.