Thuốc này rất độc.

In Vietnamese, demonstratives like này (this) usually come after the noun.

So:

• thuốc này = this medicine
• not này thuốc

This is a very common pattern:

• người này = this person
• nhà này = this house
• xe này = this vehicle

So the order is different from English: noun + this/that.

Vietnamese often does not use a verb like is when an adjective is the predicate.

So:

• Thuốc này rất độc. literally follows the pattern This medicine very toxic.

That is completely normal in Vietnamese.

You would usually use là for things like identification or definition, not before ordinary descriptive adjectives.

For example:

• Đây là thuốc. = This is medicine.
• Thuốc này rất độc. = This medicine is very toxic.

So in your sentence, leaving out is is correct.

Rất means very.

It usually goes before the adjective or descriptive word:

• rất độc = very toxic
• rất tốt = very good
• rất đẹp = very beautiful

If you remove rất, the sentence is still grammatical:

• Thuốc này độc. = This medicine is toxic.

Adding rất just makes the statement stronger.

Here, độc means poisonous, toxic, or venomous depending on context.

In this sentence, it means the medicine/substance is dangerous because it has toxic properties.

A useful comparison:

• độc = poisonous / toxic
• độc hại = harmful, toxic, damaging

Also, do not confuse this with other meanings of độc in different contexts, such as single/alone or unique in certain compounds. In Thuốc này rất độc, the meaning is clearly toxic/poisonous.

Not always. Thuốc is a broad word, and its exact meaning depends on context.

It can refer to things like:

• medicine
• drug
• remedy
• tobacco/cigarettes in expressions like thuốc lá

Examples:

• thuốc cảm = cold medicine
• thuốc lá = cigarettes / tobacco
• thuốc độc = poison

So even though the meaning has already been given to you here, it is good to know that thuốc is a flexible word.

A simple breakdown is:

• thuốc = medicine / drug
• này = this
• rất = very
• độc = toxic / poisonous

So the structure is roughly:

• medicine this very toxic

That sounds strange in English, but it is normal Vietnamese word order.

No, not here.

Thuốc này is a natural and complete noun phrase by itself.

Vietnamese often uses classifiers, but they are not required in every sentence. With thuốc, especially in a general statement like this, no classifier is needed.

You might see a longer phrase like:

• loại thuốc này = this kind/type of medicine

But in your sentence, Thuốc này is the normal choice.

The tones are:

• thuốc: sắc tone
• này: huyền tone
• rất: sắc tone
• độc: nặng tone

A few pronunciation tips:

• thuốc ends in -c, so it stops sharply.
• rất ends in -t, also with a short stop.
• độc has the heavy nặng tone and also ends in -c, so it is short and clipped.

Those final consonants are important. Vietnamese final -c and -t are much shorter than final sounds in English.

Yes, you could, but the nuance is a little different.

• độc focuses on being poisonous/toxic
• độc hại is broader and can mean harmful, toxic, or damaging

So:

• Thuốc này rất độc. sounds like a direct warning: this is very poisonous/toxic.
• Thuốc này rất độc hại. sounds a bit broader or slightly more formal.

For a simple, strong warning, rất độc is very natural.

You can do that quite easily.

Negative:

• Thuốc này không độc. = This medicine is not toxic.
• Thuốc này không độc lắm. = This medicine is not very toxic.

Yes/no question:

• Thuốc này có độc không? = Is this medicine toxic?
• Thuốc này độc không? = Is this medicine toxic?

Both question patterns are common. Learning these versions helps you see how the basic sentence works.