-ly or -ally? Basically, Accidentally, Publicly and the Rule

"Basicly." "Accidently." "Publically." All three look reasonable, all three turn up in emails every day, and all three are wrong. The trouble is not that people are careless. It is that these words are pronounced almost exactly like their misspellings. Nobody says "ba-sic-al-ly" with four crisp syllables. We say "BAY-sik-lee", and the -al- disappears in speech.

So you cannot hear the answer. You have to know where the word came from, and that turns out to be much easier than it sounds. Nearly every -ly or -ally decision comes down to one question: what is the adjective underneath the adverb?

This guide gives you that question, the handful of patterns it produces, the one famous exception, and a short list of words worth practicing until they come out right without a pause.

The rule in one line

An adverb is usually built by taking an adjective and adding -ly. Quick becomes quickly. Sad becomes sadly. Careful becomes carefully. The adjective stays whole, and -ly goes on the end.

That is the entire rule. Find the adjective, keep every letter of it, add -ly. The confusing words are the ones where the adjective is not the one you expect, or where you are not quite sure how the adjective itself is spelled.

Take "accidentally". The adjective is not "accident", which is a noun. It is "accidental". Keep every letter of "accidental", add -ly, and you get "accidentally", with the double l that so many people leave out. "Accidently" is what happens when you build the adverb from the noun instead.

The same logic gives "incidentally" from "incidental", "occasionally" from "occasional", "finally" from "final", "really" from "real", and "usually" from "usual". Each double l is simply the l of the adjective meeting the l of the ending. Nothing is being doubled on purpose. Two letters that both belong there are standing side by side.

Why you cannot hear the -al

English speech squeezes unstressed syllables. The middle of "accidentally" is said so lightly that it barely exists, and "basically" is often said in three syllables, not four. That is normal, and it happens in every accent.

The vowel in those squeezed syllables is the schwa, the vague "uh" sound that can be spelled with almost any vowel letter. It is behind a huge share of adult spelling mistakes, and we explain it fully in the guide to schwa. For -ally words, the practical lesson is this: when sound gives you no clue, meaning does. You do not need to hear the -al- if you know it belongs to the adjective.

This idea, that spelling often follows meaning rather than sound, has good research behind it. Peter Bowers, John Kirby and Hélène Deacon reviewed studies of morphological instruction in 2010, meaning teaching that shows how words are built from meaningful parts. Across 22 studies, they found that it helped learners, with particular benefits for less able readers. Seeing "accidental" inside "accidentally" is morphology at work.

The -ic family: basically, specifically, automatically

Here is the pattern that causes the most trouble. Adjectives that end in -ic almost always form their adverb with -ally, not -ly.

Basic becomes basically. Specific becomes specifically. Automatic becomes automatically. Dramatic, tragic, realistic, scientific, enthusiastic, frantic and economic become dramatically, tragically, realistically, scientifically, enthusiastically, frantically and economically.

Why the extra -al-? Many of these words once had, or still have, a twin adjective ending in -ical. "Historic" and "historical" both exist. So do "economic" and "economical", "comic" and "comical", "magic" and "magical". The adverb was built on the -ical form, and over time -ically became the normal adverb ending for the whole -ic family, even for words like "basic" that never had a common "basical" twin.

So for any -ic word, the safe default is -ally. If you write "-icly", you are almost certainly wrong. Almost.

Publicly, the famous exception

"Publicly" is the one common word that breaks the -ic rule. It takes plain -ly, not -ally. "Publically" appears in some dictionaries as a rare variant, but most usage guides treat it as an error, and in professional writing it will be read as one.

There is no satisfying reason for this. "Public" never had a widely used "publical" form, and the plain -ly adverb simply won. The honest advice is to learn it as a single exception. The useful thing about having just one is that it is easy to hold onto: every common -ic word takes -ally, except public.

You will sometimes see "politically" given as a second exception, but it is not one. "Politically" is built from "political", an -al adjective, so it follows the main rule perfectly. The adjective "politic", meaning wise or shrewd, has its own adverb, "politicly", which is so rare that most people never meet it.

When the adjective changes before -ly

The rule "keep every letter of the adjective" has three small adjustments. Each one exists to stop the word looking or sounding odd.

First, a consonant plus y changes the y to i. Happy becomes happily, easy becomes easily, busy becomes busily, and angry becomes angrily. This is the same change you see in "happier" and "studied". A few one-syllable words keep the y, at least in some styles: shyly and slyly are standard, and "dryly" is the usual American form, with "drily" more common in British writing.

Second, adjectives ending in a consonant plus -le drop the e and add only y. Simple becomes simply, gentle becomes gently, possible becomes possibly, and terrible becomes terribly. Without this change you would get "simplely", which no one says. The -le is already doing the work of a syllable, and the y finishes it.

Third, a few words ending in e lose it. True becomes truly, due becomes duly, and whole becomes wholly. These are worth memorizing as a little group, because almost every other word ending in silent e keeps it. Complete becomes completely, sincere becomes sincerely, extreme becomes extremely, definite becomes definitely, and immediate becomes immediately.

Finally, adjectives that already end in -ll add only -y, so "full" becomes "fully" and "dull" becomes "dully". Three l's in a row never happen in English.

Definitely, separately, and the other e words

Because "truly" drops its e, some people start dropping the e everywhere, and a whole family of misspellings appears: "definitly", "completly", "immediatly", "seperatly". The fix is the main rule again. The adjective is "definite", which ends in e, so the adverb is "definite" plus -ly: "definitely". The adjective is "separate", so the adverb is "separately".

Many of these words have a second trap hiding inside the adjective. "Definite" contains "finite", which is a good way to remember its i's. "Separate" has "a rat" in the middle, the oldest memory trick in the book, and it works. If you get the adjective right, the adverb takes care of itself. Our list of the hundred words adults misspell most has a trick for many of these.

The pattern also explains why "argument" loses the e of "argue" while "lately" keeps the e of "late". Different suffixes, different habits. For -ly, the default is to keep the e.

Daily, gaily and a few strays

A handful of everyday adverbs follow none of the patterns above, and they are worth knowing so they do not shake your confidence in the rule.

"Day" becomes "daily", not "dayly", and "gay" in its older sense of cheerful becomes "gaily". "Lay" and "pay" behave similarly in "laid" and "paid", as old, high-frequency words often do. There is no rule to apply here; these are words learned as wholes.

Then there are words that look like adverbs but are not built from an adjective at all. "Early" is the same word as the adjective "early". "Likely" is an adjective too, as in "a likely result". "Friendly" and "lovely" are adjectives, which is why you cannot write "she spoke friendly" in careful English and say "in a friendly way" instead. None of these change the -ly or -ally rule, but they explain why a word ending in -ly is not always an adverb.

A three-second check while you write

You will not stop mid-sentence to consult a table, and you should not have to. The whole rule fits into a short check you can run in your head before you send a message.

First, strip the -ly away and ask what is left. If what is left is an adjective you can spell, you are nearly done: "careful" plus -ly, "usual" plus -ly, "complete" plus -ly. Second, look at the last letters of that adjective. If it ends in -ic, you want -ally, unless the word is "public". If it ends in -le, swap the e for y. If it ends in a consonant and y, change the y to i. Third, if the leftover is a noun rather than an adjective, as with "accident" or "incident", look for the -al adjective that sits between the noun and the adverb.

That third step catches more errors than any other. "Accidently", "incidently" and "coincidently" all come from skipping the adjective and going straight from the noun. Once you notice that the adjective is "coincidental", "coincidentally" stops looking strange.

Run the check deliberately for a week or two and it becomes something you no longer notice doing. That is what fluency in spelling really is: the same reasoning, made so fast it feels like instinct.

How to practice so it sticks

Reading a rule once does not change what your fingers type in a hurry. The mistakes in this post are fluent mistakes: they come out fast because they sound right. Replacing them needs repeated, effortful recall.

The method that works best is the one memory researchers have tested most. Roediger and Karpicke showed in 2006 that practicing recall beats rereading for long-term memory, and a large review led by John Dunlosky in 2013 rated practice testing and spaced practice as the two most useful study techniques of the ten they examined. In everyday terms: try to produce the word from memory, check it, and come back to it after a gap.

Here is a short routine. Have someone read out, or record yourself saying, a mixed set of adverbs: basically, publicly, accidentally, truly, specifically, gently, happily, definitely, automatically, finally. Write each one without looking. Before you check, say the adjective underneath each one and whether it ends in -ic, -al, -le, -y or e. Then compare. The point of naming the adjective is to make the thinking step automatic, so that next time "basically" makes you think "basic, -ic, so -ally" in a fraction of a second.

Spelling.School works on the same principle. You hear the word, type it, see which letters went wrong, and the word comes back for review with spaced repetition. If you keep missing the same ending, such as -ly against -ally, it adds more words with that pattern until you get it.

What to do next

Write down the -ly words you know you hesitate over. For most people, the list includes basically, accidentally, publicly, specifically, definitely, truly and immediately. Next to each, write the adjective it comes from. Then, tomorrow, write the adverbs again from memory, with the adjectives covered. Repeat in three or four days.

If you would like to see which patterns you miss without noticing, the twenty-minute spelling self-audit is a good way to find them, and a few minutes a day on Spelling.School will keep bringing those words back until they are settled.

Questions people ask

Is it basically or basicly?

The correct spelling is "basically". Adjectives ending in -ic, such as basic, specific and automatic, form their adverbs with -ally, giving basically, specifically and automatically. "Basicly" is a very common misspelling because the -al- is not heard when the word is spoken.

Why is accidentally spelled with two l's?

"Accidentally" is built from the adjective "accidental", not the noun "accident". You keep every letter of "accidental" and add -ly, so the l at the end of the adjective sits next to the l of the ending. The same pattern gives "incidentally", "occasionally" and "finally".

Is publically a word?

"Publically" appears in a few dictionaries as a rare variant, but most usage guides treat it as a misspelling of "publicly". "Public" is the one common -ic adjective that takes plain -ly instead of -ally. In school, exam and professional writing, always write "publicly".

When do you add ally instead of ly?

Add -ally when the adjective ends in -ic, as in basic, tragic and scientific, which become basically, tragically and scientifically. Words that already end in -al, such as final, usual and accidental, simply add -ly, which produces the same -ally ending. Most other adjectives take plain -ly, as in quickly, sadly and carefully.

Is it truly or truely?

The correct spelling is "truly". "True" drops its final e before -ly, and so do "due" and "whole", which become "duly" and "wholly". Most other adjectives ending in silent e keep it, as in "completely", "sincerely" and "definitely", so "truly" is an exception worth memorizing.

Is it definitely or definately?

The correct spelling is "definitely". The adverb is built from the adjective "definite", which contains the word "finite", so both the middle and the end use the letter i before the final -ly. "Definately" and "definitly" are among the most common misspellings in English.

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