I promise vs Swear

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

I promise

Beyond 10,000 (less common)

Swear

Informal Top 2,000 (common) B2 verb

Most formal: I promise Most common: Swear

	I promise	Swear
Pronunciation	🇬🇧 //aɪ ˈprɒmɪs// 🇺🇸 //aɪ ˈprɑːmɪs//	🇬🇧 /["/sweə(r)/","/sweəz/","/swɔː(r)/","/swɔːn/","/ˈsweərɪŋ/"]/ 🇺🇸 /["/swer/","/swerz/","/swɔːr/","/swɔːrn/","/ˈswerɪŋ/"]/
Meaning	I will do what I say.	To use rude or offensive words.
Example	I promise to help you with your project tomorrow.	I swear to tell the truth in my testimony.
Register	Neutral	Informal
How common	Beyond 10,000 (less common)	Top 2,000 (common)
CEFR level	-	B2
Part of speech		verb
Collocations	make a promise, keep a promise, break a promise	loudly, quietly, silently, hear somebody, at, solemnly, on oath, under oath, be prepared to, make somebody, by, on, to, be sworn into office, swear somebody to secrecy, swear somebody to silence, solemnly, on oath, under oath, be prepared to, make somebody, by, on, to, be sworn into office, swear somebody to secrecy, swear somebody to silence, solemnly, on oath, under oath, be prepared to, make somebody, by, on, to, be sworn into office, swear somebody to secrecy, swear somebody to silence, solemnly, on oath, under oath, be prepared to, make somebody, by, on, to, be sworn into office, swear somebody to secrecy, swear somebody to silence
Antonyms	-	praise, compliment
Common mistakes	Confused with 'I promise you' - which adds emphasis., Using it too casually in serious situations.	Confusing 'swear' with 'promise' — they have different meanings., Using it in formal writing where it's not acceptable., Using 'swear to' instead of 'swear at' when expressing anger.
Usage notes	Used in informal and formal contexts to assure someone of a future action. Avoid in sarcastic tones.	Used in informal settings to express anger or frustration. Often considered inappropriate in formal contexts. Be cautious of the audience and setting before using.

See it in real clips

Agents of S.H.I.E.L.D. › S1 E1

-I promise. -Come on, honey.

Breaking Bad › S1 E2

Sorry. I'll do it tomorrow, I promise.

A Knight Of The Seven Kingdoms › S1 E1

Look, lad, I promise you...

Agents of S.H.I.E.L.D. › S1 E1

-I promise. -Come on, honey.

Breaking Bad › S1 E2

Sorry. I'll do it tomorrow, I promise.

I promise

I swear. All the guineas are buying it, huh?

How I Met Your Mother › S1 E1

- I swear. - I swear.

I swear. All the guineas are buying it, huh?

How I Met Your Mother › S1 E1

- I swear. - I swear.

Swear

Frequently asked questions: I promise vs Swear

What's the difference between I promise and Swear?

I promise: I will do what I say. Swear: To use rude or offensive words.

Which is more formal: I promise and Swear?

I promise is the most formal of these.

Which is more common: I promise and Swear?

Swear is the most common in everyday English.

Can you show an example of each?

I promise: I promise to help you with your project tomorrow. Swear: I swear to tell the truth in my testimony.

Can I use I promise and Swear interchangeably?

Not always. I promise and Swear 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.