Explanation:
The diagram shown in the picture is a circle with center O.
Now let try to identify the difference amongst the three terms with the help of the image.
Radius can be defined as the line that joins the center of a circle to any point on the circumference. From the image line OA or line OB is called radius.
Chord can be defined as the line that joins any two points on the circumference.The line CD denotes a chord.The chord divides the circle into minor and major segment .
Diameter can be defined as the chord that passes through the center of a circle.
We can also say that the chord that divides the circle into two equal segment is called diameter.
And also, two radii are equal to a diameter.Hence line AB (is that OA plus OB) is called a diameter.