Miller's use of language in Death of a Salesman helps to create the illusion that what we hear is real, rather than carefully crafted, speech.
Language
The language used in Death of a Salesman is also, for the most part, highly realistic, with Miller showing great skill in ensuring characters’ dialogue mimics the speech patterns of late 1940s New Yorkers.
American slang
There is heavy use of American slang of the time (“bum”, “dime a dozen”, “phony”) and Miller’s characters often stumble over their words or, when discussions become heated, become inarticulate.
At such moments they may repeat themselves (“Go back, go back…”) or break off.
Clichés
There is also the repeated use of clichés, particularly when Willy discusses his sales (“I’ll knock ‘em dead in Providence!”) which, in their banality, help to create the illusion that what we hear is real, rather than carefully crafted, speech.
Elevated language
However, Miller also elevates his characters’ language at times.
Charley uses an archaic term (“Nobody dast blame this man”) at Willy’s funeral, as if trying to give Willy’s life and death more grandeur.
Metaphor
Ben’s language also becomes highly metaphorical: his talk of the promise of “diamonds” luring Willy into taking his own life.