The "language" of film bears much similarity to the grammatical rules which govern natural language, yet it also exhibits some striking dissimilarities. In particular, the language of film is evolving at a tremendous rate, and this fact has interesting consequences for how we understand the history of cinema.
Natural language is governed by syntactic rules, rules about how its primitive elements combine in order to create meaning. In the language of film, there are many similar rules, although just as in poetry, syntactic rules can be broken in ways which enhance rather than detract from meaning.
For example, consider the 180° rule—this rule states that when editing a scene, all shots should stay on one side of an imaginary line drawn through the middle of the action. In the case of a conversation between two people, the line is typically drawn through the center of their two heads. The scene is then created out of three shots: 1. an establishing shot from the distance including both speakers; 2. a shot over the right shoulder of the lefthand speaker at the right one; 3. a shot over the left shoulder of the righthand speaker at the left one. Shots 2 and 3 show each speaker in close up, but from a vantage on the same side of the imaginary line as the establishing shot.
Just as in a line of poetry, the rules of word order can be violated in order to create rhythmic or rhyming effects, the 180° rule can be violated in order to create disorienting effects, or in order to preserve some especially interesting performance or angle. Likewise, a moving camera can "violate" the rule in a more organic manner, changing the orientation of the audience's perspective in real time.
Also as in the case of poetry, however, rule violation presupposes a savvy audience. A director who decides to violate the 180° rule succeeds in his aesthetic choice only if the audience can follow along, and interpret the spatial arrangement of the action despite it being presented in a more complex manner.
And this brings us to some dissimilarities with natural language. It is a fundamental tenet of contemporary linguistics that all natural languages are equally expressive. Of course, a newly discovered aboriginal tribe in the jungles of Papua New Guinea will most likely not have a word for "microwave" (say)—but they can always stipulate a new one. Where their language will be equally expressively powerful is in its syntactic structures. There is no arrangement of stuff which can be described in one language but not in another. In this sense, all natural languages are equal.
Not so the languages of cinema! The language of film has evolved over its short history in ways which have increased its expressive power.
Consider, for example, a camera motion which fluidly crosses the imaginary line of the 180° rule. Such a camera motion was not technically possible in the early days of film, when cameras were enormous and fixed in place. The addition of a new technical possibility expands the language of film syntactically. This is not like adding the word "micorwave" to the aboriginal lexicon, it's like handing them a new grammatical structure, one which can express ideas which could never before be voiced!
But it is not just the technical possibilities which have evolved, so also the expectations and "savvy" of the audience. Long gone are the days of an audience so naïve they could not be expected to distinguish moving image from reality. Today's audience has been educated by the fast cutting of MTV and the shaky cameras and jumpcuts of "reality" television. Along with a more sophisticated palette for expression on the side of the filmmaker goes a more sophisticated means of interpretation on the side of the audience.
Why should the language of film be so different from natural language in this regard? A simple answer is just time. While natural languages (even those of the isolated aboriginal variety) have evolved for tens of thousands of years, the language of cinema has been around a mere 120. Furthermore, this past century has witnessed the most dramatic simultaneous technological and cultural change of any period in human history, and film is right there in the thick of it, evolving at an exponential rate with human culture itself.
A Moral / The Future.
A moral here for the history of cinema is one of apples and oranges. Comparing the films of the 1920s with those of the 1990s is arguably more difficult than comparing Tang court poetry with e. e. cummings. In the latter case there are merely vast cultural divides, but in the former the issue of technological possibility—expressive power—looms large as well.
Will the language of film stop evolving? Will it reach a fixed state? When will film see its first Shakespeare, its first Goethe, its Da Vinci or Michelangelo? Who knows, but the most likely answers are: not anytime soon.