Questions about example sentences with, and the definition and usage of "Stair"

A: Escalera

A: Technically, "a stair" is one step (ступенька). A "staircase" is a collection or flight of stairs. But when we say "stairs" in the plural, it has the same meaning as "staircase."

He ran up the staircase = He ran up the stairs. (the second option is more colloquial)

He tripped over the last stair, because it was taller than the others.

A: pronunciation is the same.
Stair is a step in a staircase. “There are twelve stairs to the second floor”
Stare is a long unbroken gaze. “Cats stare at birds before they pounce”

A: In my opinion i dont think there is a difference 😊 I just think some people say staircase to sound more "fancy"

A: A stair is part of a staircase. One stair is like one step on the staircase. "Stairs" and "staircase" are very similar, but there's a slight difference. "Stairs" is used mainly when talking about direction. Ex: "Go up the stairs." And "staircase" is used more when talking about the actual object. Ex: "That home has a marble staircase"

A: A staircase is made up of many stairs

A: A stair is a single step on a staircase. A staircase and stairway are both the same thing: a set of many stairs.

A: Neither:

"I'm going downstairs."

A: Check the question to view the answer

A: Check the question to view the answer

A: 1. I tripped on the stair and fell *to* the sidewalk.
2. I tripped on the subway and fell down.

Your sentences make sense, and your 2nd sentence is perfect.
But for no. 1, we would say "... and fell to the sidewalk" or "... and landed on the sidewalk".

A: × Be careful on the stair.
✓ Be careful on the stairs. - We use the plural. If it was just one stair we would say "Be careful on the step."

× It’s steep.
✓ The stairs are steep. (or) They are steep.

I would write as one sentence: Be careful on the stairs, they are steep.

A: I tripped on the stairs while using my phone. I'm so embarrassed.

A: A staircase consists of several individual stairs. A staircase might also be called the "stairs". An individual stair is also called a "step"