So vs Therefore

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

So

High-frequency chunk A1 adverb

Therefore

Formal Top 2,000 (common) B1 adverb

Most formal: Therefore Most common: So

	So	Therefore
Pronunciation	🇬🇧 /["/səʊ/"]/ 🇺🇸 /["/səʊ/"]/	🇬🇧 /["/ˈðeəfɔː(r)/"]/ 🇺🇸 /["/ˈðerfɔːr/"]/
Meaning	used to say that something is true or to show a result	For that reason; as a result.
Example	She was tired, so she went to bed early.	He's only 17 and therefore not eligible to vote.
Register	Neutral	Formal
How common	High-frequency chunk	Top 2,000 (common)
CEFR level	A1	B1
Part of speech	adverb	adverb
Collocations	so happy, so much, so good, so far, so fast	therefore concluded, therefore it follows, therefore we can, therefore you should, therefore the result
Antonyms	not	however, nevertheless, nonetheless
Common mistakes	Confused with 'very' — 'so' indicates a result rather than degree., 'So' used incorrectly at the beginning of formal sentences., Overusing 'so' in formal writing, making the text less precise.	'Therefore' is sometimes confused with 'therefor', which has a different meaning., Learners may use 'therefore' to start a sentence in informal contexts, which can sound awkward., 'Therefore' may be incorrectly placed in a sentence away from the cause or condition.
Usage notes	Used to connect sentences, showing cause and effect. In informal contexts, it can start statements or express agreement but may be considered vague in formal writing.	Use 'therefore' to connect ideas in formal writing or speech. It’s less common in everyday conversation and can sound stiff. Avoid it in casual contexts.

Frequently asked questions: So vs Therefore

What's the difference between So and Therefore?

So: used to say that something is true or to show a result Therefore: For that reason; as a result.

Which is more formal: So and Therefore?

Therefore is the most formal of these.

Which is more common: So and Therefore?

So is the most common in everyday English.

Which is more advanced: So and Therefore?

Therefore is the highest level, at B1, on the CEFR scale.

Are So and Therefore the same CEFR level?

So: A1, Therefore: B1 on the CEFR scale.

What part of speech are So and Therefore?

So: adverb, Therefore: adverb.

Can you show an example of each?

So: She was tired, so she went to bed early. Therefore: He's only 17 and therefore not eligible to vote.

Can I use So and Therefore interchangeably?

Not always. So and Therefore 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.