First of all vs Firstly vs For one thing

When to use each in English, with meaning, register, and examples.

First of all

Top 2,000 (common)

Firstly

Formal Top 3,000 (common) A2 adverb

For one thing

Top 3,000 (common)

Most formal: Firstly Most common: First of all

	First of all	Firstly	For one thing
Pronunciation	🇬🇧 //fɜːst əv ɔːl// 🇺🇸 //fɜrst əv ɔl//	🇬🇧 /["/ˈfɜːstli/"]/ 🇺🇸 /["/ˈfɜːrstli/"]/	🇬🇧 //fɔː wʌn θɪŋ// 🇺🇸 //fɔr wʌn θɪŋ//
Meaning	To start with; the first point to mention.	At the start of a list or explanation.	One reason or point to consider.
Example	First of all, we need to discuss the budget for next year.	There are two reasons for this decision: firstly…	For one thing, it’s cheaper to travel by bus.
Register	Neutral	Formal	Neutral
How common	Top 2,000 (common)	Top 3,000 (common)	Top 3,000 (common)
CEFR level	-	A2	-
Part of speech		adverb
Collocations	first of all, we need, first of all, let's discuss, first of all, thank you, first of all, I want to, first of all, remember	firstly and secondly, firstly then, firstly I would like	for one thing, for one important thing, for one specific thing
Antonyms	-	lastly, finally	-
Common mistakes	Using it in the middle of a sentence instead of at the beginning., Confusing with 'firstly', which is more formal., Omitting 'of all' and saying only 'first'.	'Firstly' is not often used in informal contexts., Some learners confuse 'firstly' with 'first,' thinking they can use them interchangeably in all situations., Overusing 'firstly' when listing items can sound overly formal.	Using it without context, making it unclear., Incorrectly following it with unrelated statements., Confusing it with similar phrases like 'for one reason'.
Usage notes	Often used to introduce the first point in a list. Appropriate in both spoken and written contexts. Avoid in very formal settings.	Use 'firstly' to introduce the first point in formal writing or speeches. Avoid in casual conversations; 'first' is often preferred instead.	Use this phrase to introduce a reason or point in discussions. It's often used informally but can be appropriate in more serious contexts as well.

See it in real clips

Avengers › Avengers Endgame

First of all, that's horrible.

Agatha Christies Poirot › S1 E1

First of all. . .

Yes. First of all, you're all done.

Avengers › Avengers Endgame

First of all, that's horrible.

Agatha Christies Poirot › S1 E1

First of all. . .

First of all

Avengers › Avengers Endgame

The Aether, firstly, is not a stone.

The Lord Of The Rings › The Fellowship Of The Ring

Do you know how the Orcs first came into being?

Avengers › Avengers Endgame

The Aether, firstly, is not a stone.

The Lord Of The Rings › The Fellowship Of The Ring

Do you know how the Orcs first came into being?

Firstly

Avengers › Avengers Infinity War

Well, for one thing, I'm not asgardian.

For one thing

Frequently asked questions: First of all vs Firstly vs For one thing

What's the difference between First of all, Firstly, and For one thing?

First of all: To start with; the first point to mention. Firstly: At the start of a list or explanation. For one thing: One reason or point to consider.

Which is more formal: First of all, Firstly, and For one thing?

Firstly is the most formal of these.

Which is more common: First of all, Firstly, and For one thing?

First of all is the most common in everyday English.

Can you show an example of each?

First of all: First of all, we need to discuss the budget for next year. Firstly: There are two reasons for this decision: firstly… For one thing: For one thing, it’s cheaper to travel by bus.

Can I use First of all, Firstly, and For one thing interchangeably?

Not always. First of all, Firstly, and For one thing are related and overlap in some contexts, but they differ in register, how common they are, and usage, so swapping one for another can change the meaning or tone. Check the differences above before substituting.