Widescreen

Anything wider than 4:3.

Any aspect ratio wider than 4:3 is commonly referred to as “widescreen.” HD is natively widescreen by definition because of its 16:9 aspect ratio.

Widescreen can be achieved in SD by letterboxing which shows the full width of the original material.

 

widescreen vs. 4x3

Fig 1. widescreen vs. 4×3