Three student attempt to define what a line segment it?
Definition of a line segment
Duru's definition: A line segment is a line connecting two endpoints
Oliver's definition: A line segment is when three points are all on the same line.
Carlos' definition: A line segment is part of a line, not the whole thing.
Teacher comments
*I think you have the right idea, but you need to be more careful with your language.
*What you've written is true, but it isn't a correct definition. A ray would also fit your defenition
*Were you thinking of the team collinear?

Got to match the teacher comment to the three students definition.

First definition:

Duru's definition: A line segment is a line connecting two endpoints

                                               ⇅

Teacher's comment: What you've written is true, but it isn't a correct definition. A ray would also fit your defenition

Second definition:

Oliver's definition: A line segment is when three points are all on the same line.

                                                ⇅

Teacher's comment: Were you thinking of the team collinear?

Third definition:

Carlos' definition: A line segment is part of a line, not the whole thing.

                                               ⇅

Teacher's comment: I think you have the right idea, but you need to be more careful with your language.

Explanation:

A line segment is part of a line that connects points. It limited consequently, it has length.

Duru's definition: A line segment is a line connecting two endpoints

                                               

It is missing that it is just a part of the line. A ray also connects two points but extends infinetly in one direction. Thus,  Duru's definition is not so specific.

That justifies teacher's comment:

Teacher's comment: What you've written is true, but it isn't a correct definition. A ray would also fit your defenition

Second definition:

Oliver's definition: A line segment is when three points are all on the same line.

 

The constraint of a line segment to three points all on the same line corresponds to collinear points. Two points always form a line,, but three points lie on a line only in they are collinear.

That justifies, theacher's comment:                          

Teacher's comment: Were you thinking of the team collinear?

Third definition:

Carlos' definition: A line segment is part of a line, not the whole thing.

Mathematicall language is formal. You must use precise words. An expression as 'whole thing" is not formal.

That justifies teacher's comment:

Teacher's comment: I think you have the right idea, but you need to be more careful with your language.

No one will ever know..