How does the language in Act III, scene 4 reflect the characters?
As the coronation banquet is about to commence(act3 sc.4), Macbeth addresses his guests in a language and tone that suggest formal poise and decorousness:'You know your own degrees; sit down:/ At first and last a hearty welcome'. Lady Macbeth also exudes friendly hospitality to corroborate her husband's words like an ideal hostess.
But as the first murderer appears at the door and Macbeth approaches to him, there is a tone of hushed caution in Macbeth's words:'There's blood upon thy face'. Soon thereafter when Macbeth comes to know that Fleance has escaped though Banquo is killed, his language shows paroxysm of fear:[Aside]'Then comes my fit again:I had else been perfect.............'. The murderer speaks an idiom of cold professional cruelty, characteristic of his status and vocation.
After the exit of the murderer, Lady Macbeth speaks accusingly to remind her husband of his discourteous indifference to the assembled guests:'My royal lord,/ You do not give the cheer: the feast is sold..........'. Then the ghost of Banquo appears to Macbeth responding ironically to his recalling of Banquo, and Macbeth's words get instantly soaked with visionary fear:'Thou canst not say I did it: never shake/ Thy gory locks at me'.
From this moment till the abandonment of the banquet, Macbeth's language betrays his fear-stricken mind as he keeps addressing the blood-boltered spectral image of Banquo, e.g.'Avaunt! and quit my sight!let the earth hide thee!' or 'What man dare, I dare:/ Approach thou like the rugged Russian bear.............'.
Lady Macbeth uses her language sarcastically to bring her husband back to normal sense:'This is the very painting of your fear.........../ O, these flaws and starts,/ Impostors to true fear would well become/ A woman's story at a winter's fire...........'.
At the end of the scene, after the departure of the guests, Macbeth sounds rather a bit delirious:'It will have blood:they say blood will have blood:/ Stones have been known to move and trees to speak;/ Augures and understood relations have/ By maggot-pies and choughs and rooks brought forth/ The secret'st man of blood'. Lady Macbeth switches over to softer and more sympathetic tone:'You lack the season of all natures, sleep'.
At the beginning of the Act 3 scene 4 he acts too posh " You all know your degrees" but toward the end he starts going crazy.