Poisonous vs Toxic

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

Poisonous

Top 5,000 (fairly common) B1 adjective

Toxic

Top 2,000 (common) C1 adjective

Most common: Toxic

	Poisonous	Toxic
Pronunciation	🇬🇧 /["/ˈpɔɪzənəs/"]/ 🇺🇸 /["/ˈpɔɪzənəs/"]/	🇬🇧 /["/ˈtɒksɪk/"]/ 🇺🇸 /["/ˈtɑːksɪk/"]/
Meaning	Something that can make you sick or kill you.	something harmful or poison.
Example	poisonous chemicals/fumes/plants	**toxic chemicals/fumes/gases/substances**
Register	Neutral	Neutral
How common	Top 5,000 (fairly common)	Top 2,000 (common)
CEFR level	B1	C1
Part of speech	adjective	adjective
Collocations	be, become, deadly, extremely, highly, to, be, become, deadly, extremely, highly, to	be, prove, stay, extremely, fairly, very, to, be, prove, stay, extremely, fairly, very, to, be, prove, stay, extremely, fairly, very, to
Antonyms	safe, harmless	wholesome, harmless, beneficial
Common mistakes	Confusing 'poisonous' with 'venomous'., 'Poisonous' used with inanimate objects like 'poisonous gas' can be misused in some contexts.	Confusing with 'tactile' which relates to touch., Using 'toxic' to describe something mildly annoying, instead of harmful., Mispronouncing as 'toxick' instead of 'tok-sik'.
Usage notes	Use 'poisonous' to describe plants or animals that can harm people. It's appropriate in scientific contexts and everyday discussions, but be careful not to confuse it with 'venomous', which applies to animals that inject poison.	Typically used to describe substances, relationships, or environments that are harmful. Avoid using in casual settings when discussing minor issues.

See it in real clips

The Lord Of The Rings › The Fellowship Of The Ring

The very air you breathe is a poisonous fume.

Poisonous

Breaking Bad › S1 E1

These chemicals and their fumes are toxic.

Toxic

Frequently asked questions: Poisonous vs Toxic

What's the difference between Poisonous and Toxic?

Poisonous: Something that can make you sick or kill you. Toxic: something harmful or poison.

Which is more common: Poisonous and Toxic?

Toxic is the most common in everyday English.

Which is more advanced: Poisonous and Toxic?

Toxic is the highest level, at C1, on the CEFR scale.

Are Poisonous and Toxic the same CEFR level?

Poisonous: B1, Toxic: C1 on the CEFR scale.

What part of speech are Poisonous and Toxic?

Poisonous: adjective, Toxic: adjective.

Can you show an example of each?

Poisonous: poisonous chemicals/fumes/plants Toxic: **toxic chemicals/fumes/gases/substances**

Can I use Poisonous and Toxic interchangeably?

Not always. Poisonous and Toxic 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.