Is there a difference between the two? Can we use one as a synonym to the other?

  • 7
    Please look those up in a dictionary before positing.
    – Lambie
    Mar 23 at 15:24
  • @Lambie. This question is a good one, and no dictionary definition would provide a comprehensive answer.
    – Jaime
    Mar 23 at 16:38
  • 2
    @Jamie Nevertheless the OP should still look those up in a dictionary before posting. And then refer to the dictionary definitions in their answer. It is a bad question as it stands it could be a good question, but it isn't one yet.
    – James K
    Mar 23 at 17:58
  • I understand your point.
    – Jaime
    Mar 23 at 18:04

3 Answers 3


There are distinct definitions of the two, but there is also some overlap. A poison is a toxic substance, and toxic substances can be poisonous! The study of poisons is toxicology.

  • Poisons are substances that cause harm to organisms when sufficient quantities are absorbed, inhaled or ingested.
  • A toxin is a poisonous substance produced within living cells or organisms.


So by that definition, your own body could produce toxins within you that cause harm. But anything from an external source - including toxic substances produced by other living organisms - is a poison to you.

Some also point out a distinction between venoms and poisons - both are still 'toxic' substances, the only difference is that you ingest a poison, whereas a venom is administered to you. For example, a poisonous plant may poison you if you eat it, but a snake may have to bite you to inject you with its venom.

  • Interesting that your answer contains the same reference link as mine.
    – Jaime
    Mar 23 at 16:51
  • @jaime Why don't you tell me which dictionary you use and I'll avoid ever quoting from that, too? I brought out salient points from the reference that you didn't, and I went for a direct, plain English answer to the question. I found your answer to be largely unhelpful, musing about things you were "pretty sure" of and not really getting to the point. (Also, I never followed your link and, believe it or not, I found the reference from a ddg search).
    – Astralbee
    Mar 24 at 8:27
  • You're absolutely entitled to express your opinion on my answer but I'll abstain from returning the favour. How you found the link is irrelevant.
    – Jaime
    Mar 24 at 8:37
  • @Jaime So what was the meaning of your comment? If you really found it "interesting" I hope you upvoted! But I suspect it was disingenuous.
    – Astralbee
    Mar 24 at 9:01
  • I think I've made my point quite clearly. If you'd like me to spell it out for you, we can take it out to a chat area. If not, then this conversation is closed as far as I'm concerned.
    – Jaime
    Mar 24 at 9:05

Technically, many scientists reserve the word "toxin" and the adjective "toxic" for poisons that are organic in origin (even if they are created synthetically).

In common speech, though, the words 'toxin' and 'poison' (and 'toxic' and 'poisonous') are used interchangeably as far as I know.

I'm pretty sure no non-specialists would quibble if you said "Lead is highly toxic", for example.

Indeed not even all scientists use this distinction, which is why some use the term 'bio-toxin' for poisons of biological origin.


As Kate Bunting (see comments below) points out, at least in some technical contexts, a venom and a (biological) poison are two different types of toxin. Apparently, venom enters your body when an animal injects it into you, while a poison is something you eat or breathe in.

Interestingly, at least some (but not all) venoms are considered non-poisonous because they would break down normally in your stomach if you swallowed them accidentally.

But, despite all this complication, in normal conversation you're safe enough to use "poisonous" and "toxic" as synonyms.

  • 1
    Also, a poison is swallowed or inhaled and venom is injected via a bite - but we talk about 'poisonous snakes' in everyday speech. Mar 23 at 16:01
  • @Kate Bunting: excellent point, which I'd forgotten. So officially a venom is not a poison, but it is a toxin. If you don't mind, I'll edit my answer to reflect that!
    – Jaime
    Mar 23 at 16:10
  • 3
    @Jaime - It also important to note that the words toxic, poisonous, and venomous do not necessarily preserve the meanings of their source words toxin, poison, and venom. Bill's toxic personality won't poison anyone.
    – EllieK
    Mar 23 at 16:38
  • @EllieK; Thanks for that tip. I appreciate it! ;-)
    – Jaime
    Mar 23 at 18:05

There is very little difference in meaning, when used by normal English speakers to describe substances. Lead, cyanide, fungus, Carbon monoxide, sarin, bleach... all could be described as both poisonous or toxic

The dictionary definition of "toxic" is poisonous.

There are some differences in the extended senses. For example one might talk about a "toxic relationship" (a romantic relationship that causes significant harm to one or both people involved) but "poisonous words" (bitter and spiteful comments). In these contexts, "toxic" seems to mean "harmful over a longer period of time". Idiomatically one talks about "toxic masculinity" and not "poisonous masculinity".

But when talking about substances, there is no real difference in meaning.

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