The middle part of a pair of spectacles is called a bridge or a nose bridge. This is the part of the spectacle frame that forms a bridge from one side of your nose to the other.
It is called the ordinate.
Those numbers are called factors. A pair of those is called a factor pair.
There is no specific name - other than what you used: "a pair of parallel line segments".
The pair of numbers used to locate a point on a grid is called coordinate points.
They are called a linear pair.
a pair of spectacles
A pair of spectacles is a pair of lenses set in a frame worn on the nose and ears in order to correct deficiencies in eyesight.
Spectacles, goggles, Coke-bottle bottoms
A Pair of Spectacles - 1908 was released on: USA: 23 November 1908
Frame
A pair of spectacles, or a monocle.
The noun spectacles is a shortened form for the term 'pair of spectacles'. The plural form is two pairs of spectacles.The nouns spectacles belongs to a group of nouns that are a shortened form for 'a pair of', for example:binocularsglassespantsscissorsshearsshortsspectaclestongstrouserstweezersAll of these nouns are made plural by changing 'a pair of...' to 'pairs of...'.
If a person is wearing spectacles it means he is wearing a pair of glasses. The word spectacles is rarely used in this day and age.
The curved glass in a pair of spectacles is called a lens. You will find that most spectacles are fitted with plastic lenses rather than glass lenses. The curvature of the lens determines the power/prescription/lens strength. Lens thickness, weight and curvature will vary from person to person depending on what type of prescription they need.
"Spectacles" can refer to eyeglasses worn to improve vision, or a notable display or performance.
Pince-nez is what this type of glasses is called. The name comes from French, meaning "Pinch nose".
"SPECTACLES" means when a batsman gets out on 'duck' (i.e. gets out without scoring a single run in both innings of a Test match) he is said to have scored a PAIR or in other words that batsman is said to be wearing SPECTACLES (cos the 2 round lens resemble a pair of spectacles). When batsman is out for zero in 1st innings and when he comes into bat for 2nd innings...commentator would say "And XYZ .. He is ON A PAIR" (that means he is facing the probability of making a pair) and if he indeed gets out 2nd time also... he would have actually SCORED a PAIR.