Just label it with a symbol of your choice and that is its name! Some people prefer a lower case letter but that is not a necessity.
827/1000 is another way of writing it
It's not clear from the question whether 'P' is the center of the circle, or maybe the circumference.The distance from the center to the midpoint of AB is 8 mm.The distance from the midpoint of AB the rest of the way to the circumferenceof the circle is 2 mm.
In a triangle ABC, they are AB, BC and CA.
Cylinder
Line BA
After is one English equivalent of 'ab'. Away fromis another equivalent. Either way, the Latin word 'ab' is a preposition whose object is in the ablative case.
If "AB" was her last name before she married, then "AB" is her maiden name.
Ge is another way to name germanium.
segment AB
Ab Abspoel's birth name is Albert Abspoel.
You pronounce it the A and R then Ab together A-R-AB
There is no simple way of factorising AB - CD
Ab Jenkins's birth name is David Abbott Jenkins.
Ab Taylor's birth name is Albert Snow Taylor.
Ab Harrewijn's birth name is Albert Bastiaan Harrewijn.
Ab Osterhaus's birth name is Albertus Dominicus Marcellinus Erasmus Osterhaus.