And it is an imitation of action, and especially because of this, of the men acting.
Third, the “thought”.
And this is the ability to say suitable and appropriate things, which indeed, in the case of words , is the work of the politician and rhetorician. For the ancients crafted people  who spoke politically and moderns, rhetorically. And “character”  is the sort of thing which clarifies choice, the sort [of choice] in which a person is not clear whether he choose or flee; wherefore those speeches do not have “character” in which there is nothing at all which the speaker chooses or flees. But “thought” is in those [speeches] that declare how something is or is not, or what it is generally considered [to be].
And fourth, of the things under “language”, is diction. As was said previously, I mean “diction” to be expression through language which, in the case of meter and the case of prose, has the same capability.
And of the remaining matters, song craft is the greatest of the ornamentations; but the persuasive visual element is most unskillful and the least natural to the poetic craft, for tragedy is powerful even without the assembly and the actors, and moreover the skill of the fabricator (or 'costumier') is more authoritative as regards creating of the visuals than the skill of the poetic-crafters.
7. These things having been defined then, after these matters, let us say what sort of arrangement is necessary for the arrangement of the actions, since this is the first and most important element of tragedy.
And it was laid down by us that tragedy is an imitation of a whole and complete action possessing some magnitude; for something is whole and has not magnitude.
And, something whole possesses a beginning, middle and end: and the beginning is that which is not by necessity after something else, after this some other thing comes to be or to become; and the end is that other sort of thing which comes to be after something else either by necessity or as in the majority [of the time], and after this there is nothing else; and the middle is that thing which is after another thing and after it [there are] other things.
It is necessary for the stories to be well arranged, neither happening to begin from wherever nor chancing to end at whatever point, but to express the forms that have been discussed.
Moreover since the beautiful—in respect to both an animal and whatever sort of deed which came together from some [causes]—it is not only necessary to have the arranged things , but also the magnanimity possessed not by chance occurance; for the beautiful is in both the magnanimity and the arrangement. Wherefor neither the very small should become a beautiful animal (for since the vision [of it] occurs in a nearly unfelt extent of time it is confused) nor should the very large (for the vision [of it] does not happen all at the same time, but the single and whole thing is gone from the vision of those who see it if for example the animal should be a thousand stades long).
 epi (LSJ, A.I.2.f: “in the case of” or A.III.4: “in respect of,” “concerning”) twn logwn
 I think this means people in the plays – ie., the “doing” or “acting” men of the first sentence.  The LSJ definition of “ηθος” for Aristotle is dramatis persona, so “character” in the sense of drama.
 One translation says “enrichments”. The root of the word is the idea of sweetening something.
 Ar. is making a negative rhetorical argument: the costumier (for instance) has more say over the visual elements of the play than does the writer of the tragedy, so how can something that our hero, the guy who “synthesizes the plot elements,” has no control over be an essential part of tragedy?
 I understand this to mean, essentially, “fate” or “destiny” which Ar. validates in the next phrase—he is contrasting the things that must necessarily happen to someone, and the things that they make happen by their “magnamity” in action.
 Making use of the possessive dative; not sure this is correct.