Translation guide
The English word 'poisonous' refers to something that causes harm or death when ingested, touched, or otherwise introduced into the body. In Japanese, the most common equivalent is 有毒な (yūdoku na), but natural expression often depends on whether you're talking about animals, plants, chemicals, or figurative speech.
Describing a substance, plant, animal, etc. that contains poison and can cause harm if ingested or touched.
The standard adjective for 'poisonous/toxic'. Used for chemicals, plants, animals, gases, etc. It is a na-adjective.
このキノコは有毒です。
This mushroom is poisonous.
Poisonous gas was generated.
A more colloquial phrase meaning 'having poison'. Often used in everyday speech for animals or plants.
毒のあるヘビに気をつけて。
Watch out for poisonous snakes.
Means 'toxic' or 'of poisonous nature'. More technical, often used in scientific contexts.
この物質は毒性が強い。
This substance is highly poisonous.
Specifically for creatures that deliver poison through a bite or sting.
Literally 'to possess poison'. Commonly used for venomous snakes, spiders, etc.
毒を持つクモがいる。
There are poisonous spiders.
Also works for venomous animals, though it's broader.
有毒なサソリに刺された。
I was stung by a poisonous scorpion.
Describing words, ideas, atmospheres, etc. that are metaphorically poisonous.
Means 'harmful' or 'noxious'. Used for negative influences, comments, environments.
有害な噂を流す。
Spread poisonous rumors.
Means 'venomous' or 'spiteful' in a figurative sense, often for speech or attitude.
彼の毒々しい言葉に傷ついた。
I was hurt by his poisonous words.
Specifically for food or drink that is contaminated or naturally toxic.
A simple, natural way to say 'poisonous if eaten'.
そのベリーは食べると毒だよ。
Those berries are poisonous if you eat them.
Means 'to cause food poisoning'. Used for bacteria or spoiled food.
この魚は食中毒を起こすことがある。
This fish can be poisonous (cause food poisoning).
有毒 is an adjective meaning 'poisonous', while 毒性 is a noun meaning 'toxicity' or 'poisonous property'. You can say 有毒な物質 (poisonous substance) or この物質は毒性がある (this substance has toxicity).
In English, 'poisonous' often implies ingestion or touch, while 'venomous' implies injection. Japanese does not strictly distinguish them; 有毒 can cover both. Use context or specify 毒を持つ (has poison) for venomous creatures.