Breakdown of В этот лифт нельзя входить.
этот
this [f: эта, n: это]
в
in / to (direction)
нельзя
one must not
входить
to enter
Questions & Answers about В этот лифт нельзя входить.
Why do we use the imperfective verb входить here instead of the perfective войти?
When нельзя is followed by an imperfective verb like входить, it means "it is forbidden" or "you must not". If we used the perfective войти, it would mean "it is physically impossible" (for example, if the elevator doors were jammed). Since this is a rule or prohibition, we use the imperfective.
The prefix в- in входить already means "into". Why do we also need the preposition в before the elevator?
In Russian, the preposition often "echoes" the verb's prefix. Verbs of motion starting with the prefix в- (entering) almost always pair with the preposition в (into) to show exactly what you are entering.
What case is этот лифт in, and why doesn't it change its ending?
It is in the Accusative case because it indicates the destination or direction of your motion. Since лифт (elevator) is a masculine, inanimate (non-living) noun, its Accusative form looks exactly the same as its dictionary (Nominative) form.
Why does the sentence start with в этот лифт instead of putting it at the end?
Russian word order is flexible and uses the beginning of the sentence to establish the main topic. Starting with в этот лифт highlights what we are talking about: "As for this elevator, you must not enter it."