You can name any shape or object in any way you like as long as you say what you are doing.
You can call it anything you like.
sphere
name a line that is not contained in plane N.
postulates
It is just another name for an angle.
Euclidean geometry, non euclidean geometry. Plane geometry. Three dimensional geometry to name but a few
You can call it anything you like.
Not sure about a name, but "an infinite surface with zero curvature" is an equivalent phrase.
jet plane
It usually names a line.
Istanbul the capital of Turkey name begins with the letter I.
To show that the word with the capital letter has some importance. You capitalize your name because your name is important.
The capital of Norway, which is Oslo.
Phoenix
Islamabad is the capital city in Pakistan.
The abbreviation of units is usually written with a capital letter, if it is based on the name of a person.
supermarket does not have a capital letter unless it is the name of a supermarket like Asda or Tesco.