Sentence:  The `` moving '' picture of the train or the wave coming at the audience is , to be sure , more intense than a still picture of the same subject , but the difference is really one of <WSD>degree</WSD> ; the cinematic element of time is merely used to increase the realism of an object which would still be reasonably realistic in a still photo . 
Meaning of the word marked with <WSD> tags:  a position on a scale of intensity or amount or quality