In Chapter 34, Miss Crawley invites her nephew, James Crawley, to dinner with Lady Jane and Pitt Crowley. James is a young Oxford student, awkward and a bit brash, and Thackeray stuffs his dialogue with a combination of dialect and allusion in order to satirize his behavior:
“Come, come,” said James, putting his hand to his nose and winking at his cousin with a pair of vinous eyes, “no jokes, old boy; no trying it out on me. You want to trot me out, but it’s a no go. In vino veritas, old boy. Mars, Bacchus, Apollo virorum, hay? I wish my aunt would send down some of this to the governor; it’s a precious good tap.”
As James struggles to make a favorable impression at the party, his character emerges as a brutal satire of a posh Oxford man posturing sophistication and masculinity: James inflects his speech with the mannerisms of a cocky upper-class dialect, referring to his cousin repeatedly as "old boy" and stringing together a series of nonsensical classical allusions that underscores his elite education even as it affirms his state of intoxication. "In vino veritas" is Latin for "In wine, there is truth," and Mars, Bacchus, and Apollo are all Greco-Roman gods, but there isn't much to be said about these remarks—they simply underscore that, in wine, James has revealed his lack of personality.
In Chapter 55, Becky's household staff and landlord confront her about her financial situation: in order to continue living the high life in London, she has neglected to pay either party. Thackeray uses dialect to highlight the class disparity between Becky, the erstwhile socialite, and Raggles, her landlord—and formerly the butler for Becky's husband's family:
‘O Mam,’ said Raggles, ‘I never thought to live to see this year day, I’ve known the Crawley family ever since I was born. I lived butler with Miss Crawley for thirty years; and I little thought one of that family was a goin’ to ruing me – yes, ruing me’ – said the poor fellow, with tears in his eyes. ‘Har you a goin’ to pay me? You’ve lived in this ’ouse four year. You’ve ’ad my substance: my plate and linning. You ho me a milk and butter bill of two ’undred pound, you must ’ave noo-laid heggs for your homlets, and cream for you spanil dog.’
Through manipulating punctuation, spelling, and grammar, Thackeray gives Raggles's dialogue an unmistakable roughness that contrasts with the affected refinement of Becky's own speech. There is a considerable amount of situational irony to this distinction: while Becky may appear refined, it is Raggles who has ascended the ranks of society. After leaving the service of the Crawley family, he has opened his own food shop and acquired a house to rent out—while Becky has driven Rawdon and herself to ruin by vastly overextending their means in order to maintain a façade of gentility.
In Thackeray's England, dialect is an inextricable part of class differentiation and social stratification. That comes across throughout Vanity Fair, where Thackeray has written the dialogue of a variety of his characters in dialects that represent their regional identity and their social status.