Learn Hardcore Russian: Этот мост безопасный.

мост – nominative singular, masculine noun; it is the subject.
безопасный – nominative singular, masculine adjective; it is the predicate and must agree with the subject in:
- gender (masculine),
- number (singular),
- case (nominative).

Pattern:
[Subject in nominative] + [Predicate adjective in nominative]
e.g. Мост новый., Дом большой., Город красивый.

Why is it этот мост, not это мост?

Этот is the masculine form of “this”, and мост is a masculine noun.

Forms of “this” (demonstrative pronoun/adjective) in the nominative:

этот – masculine (этот мост – this bridge)
эта – feminine (эта машина – this car)
это – neuter (это окно – this window)
эти – plural (эти мосты – these bridges)

Это also has a special use as “this is / that is”:

Это мост. – This is a bridge.

But when directly modifying a masculine noun, you need этот мост, not это мост.

Why is безопасный masculine, not безопасная or безопасное?

Adjectives in Russian must agree with the noun they describe in gender, number, and case.

мост is masculine, singular, nominative.
Therefore, the adjective must be masculine, singular, nominative: безопасный.

Other forms:

безопасная дорога – a safe road (feminine)
безопасное место – a safe place (neuter)
безопасные мосты – safe bridges (plural)

Can I also say Этот мост безопасен? What is the difference?

Yes, Этот мост безопасен. is also correct.

Difference:

Этот мост безопасный. – uses the long form adjective (безопасный).
Этот мост безопасен. – uses the short form adjective (безопасен).

General tendencies:

Long form (безопасный) is neutral, very common in speech, and can be both attributive and predicative:
- Этот безопасный мост – this safe bridge (before the noun)
- Этот мост безопасный. – this bridge is safe.
Short form (безопасен) is used only as a predicate (after the subject), often a bit more formal or bookish and can sound more like a statement of fact or conclusion:
- Этот мост безопасен для пешеходов. – This bridge is safe for pedestrians.

In everyday spoken Russian, Этот мост безопасный. is very natural; Этот мост безопасен. sounds a bit more “careful” or formal, but both are correct.

Why does безопасный end in -ый and not -ий or -ой?

For most hard-stem adjectives in the masculine nominative singular, the normal ending is -ый.

Simplified patterns:

After a hard consonant (like н in безопасн-), you usually get -ый:
- новый, старый, русский, безопасный.
After a soft consonant or certain stems, you often see -ий:
- синий (blue), последний (last), хороший.
-ой usually appears when the stress is on the ending:
- большой, молодой.

So безопасный follows the common hard-stem pattern with -ый.

Can I say Этот безопасный мост instead? Does that mean the same thing?

Этот безопасный мост is grammatical, but it means something slightly different.

Этот мост безопасный.
– This bridge is safe. (a full sentence, bridge = safe)
Этот безопасный мост…
– This safe bridge… (a noun phrase; you need more to make a complete sentence, e.g.
Этот безопасный мост построили в прошлом году. – This safe bridge was built last year.)

So:

Adjective after the noun (мост безопасный) → typically a predicate (“is safe”).
Adjective before the noun (безопасный мост) → typically a descriptor (“a safe bridge”).

Can I drop этот and just say Мост безопасный?

Yes, you can say Мост безопасный.

Meaning:

Мост безопасный. – The bridge is safe.
This would normally be understood as talking about “the bridge” that is already known from context.

Using этот (= this) points to a specific bridge near you or just mentioned:

Этот мост безопасный. – This bridge is safe (the one we’re looking at / talking about).

So you choose этот when you want to emphasize “this one right here / that one you know about.”

How do I ask “Is this bridge safe?” in Russian using this sentence?

The easiest way is to keep the same word order and change only the intonation:

Этот мост безопасный? – Is this bridge safe?
(Rising intonation at the end; very natural in speech.)

Other options:

Этот мост безопасен? – same meaning, with the short adjective form.
More formal, with the particle ли:
- Этот мост безопасный ли? – grammatically possible but sounds old-fashioned or poetic.
- Better: Этот мост безопасный или нет? – Is this bridge safe or not?

What is the difference between безопасный and надёжный about a bridge?

Both can describe a bridge, but they focus on slightly different ideas:

безопасный мост – a safe bridge: it does not present danger; you won’t fall, it won’t collapse on you, it’s safe to use.
надёжный мост – a reliable/sturdy bridge: well-built, strong, durable, unlikely to fail.

Often, a надёжный мост is also безопасный, but:

If a bridge might collapse, you’d say:
- Мост опасный / небезопасный. – The bridge is dangerous / unsafe.
If it just looks a bit old but is still structurally fine, someone might reassure you:
- Он надёжный, не переживай. – It’s reliable, don’t worry.

How do I say “This bridge is not safe” based on this sentence?

You can negate it with не:

Direct negation:
- Этот мост не безопасный. – This bridge is not safe.
  (neutral; just denies safety.)
Using the single word небезопасный (more like “unsafe”):
- Этот мост небезопасный. – This bridge is unsafe.
  (often implies some real risk or concern.)
With the short form:
- Этот мост небезопасен. – This bridge is unsafe.
  (more formal/literary.)

If the bridge is actively dangerous, many speakers will simply say:

Этот мост опасный. – This bridge is dangerous.