Bu kimyasal tehlikelidir.

This chemical is dangerous.

Breakdown of Bu kimyasal tehlikelidir.

• olmak: to be
• bu: this
• tehlikeli: dangerous
• kimyasal: the chemical

Questions & Answers about Bu kimyasal tehlikelidir.

What does the suffix -dir do in tehlikelidir?

The -dir suffix is the third-person copula (the equivalent of “is”) in formal/written Turkish. It turns the adjective tehlikeli (“dangerous”) into a complete predicate “(it) is dangerous.” In everyday spoken Turkish you can drop it:
Bu kimyasal tehlikeli.

Why isn’t there a separate word for “is” in the sentence?

Turkish usually expresses “to be” by either suffixing -dir (in writing/formal speech) or omitting it entirely (in informal speech). You don’t use a standalone verb like is.

What part of speech is tehlikeli and how is it formed?

Tehlikeli is an adjective meaning “dangerous.” It’s built from the noun tehlike (“danger”) plus the adjective-forming suffix -li, which turns many nouns into adjectives.

How would you make the sentence negative (“This chemical is not dangerous”)?

Attach the negation değil after the adjective (and before -dir if you keep it):
Bu kimyasal tehlikeli değildir.
In casual speech you usually drop -dir:
Bu kimyasal tehlikeli değil.

How can I ask “Is this chemical dangerous?”

Insert the question particle mi after the adjective. With -dir you get:
Bu kimyasal tehlikeli midir?
Without -dir (colloquial):
Bu kimyasal tehlikeli mi?

Why is bu used here, and what about şu or o?

Bu means “this” (something close to the speaker).
Şu means “that” (a bit farther away, maybe near the listener).
O means “that” (far from both).
You choose based on how near or far the object is.

What is kimyasal here—noun or adjective?

In this sentence kimyasal is a noun meaning “chemical.” It comes from kimya (“chemistry”) plus the noun/adjective-forming suffix -sal. It can also function as an adjective (e.g. kimyasal reaksiyon = “chemical reaction”).

Can I strengthen the meaning to “very dangerous”?

Yes—place an intensifier before the adjective:
Bu kimyasal çok tehlikelidir. (very dangerous)
You can also say oldukça tehlikelidir (quite dangerous) or fazlasıyla tehlikelidir (overly dangerous).

Do I need any case or number suffixes on kimyasal?

No. As the subject of a nominal sentence (subject + predicate), kimyasal stays in the bare nominative. It’s singular here, so you don’t add a plural suffix.