"casual language" is a correct and usable phrase in written English.
You can use it to refer to conversation and writing that is generally relaxed, friendly, and informal. For example, you might say, "I find that casual language is often more effective than formally written language in emails to colleagues."
Casual language used to describe mental illness is decidedly negative.
They barked in the casual language of enforcers: You wanna go?
People speak differently for interviewers than they do among themselves, and modern linguists have techniques for eliciting people's casual language that did not exist in 1962.
Casual language need not be careless or crude, and The Times, like other institutions of the written word, remains devoted to maintaining two principal standards.
The film presents a strikingly black version of the story, partly through the narrative devices of Mr. Burns and his writer, Geoffrey C. Ward, but more through the casual language of some of the commentators.
A swaggering heir to Frank O'Hara, Myles is a fabulously casual language technician, brilliant on everything from love and politics to those plastic jars of honey that are shaped like bears.
The door between literature and everyday language has long been ajar; even in casual exchanges, Afghans rely on allegory, metaphor, parables and jokes to convey meaning.
Most of the story is rendered in casual contemporary language rather than poetry.
The dancers seem entirely at home in the movement, in both its formal sophistication and casual body language.
Pike's dissonantly casual body language in the context of violence brings to mind the photos from Abu Ghraib; Lynndie England smiling and giving the camera a thumbs-up in front of tortured prisoners.
Although the narrator throws out snatches of verse at moments of heightened drama, and occasionally even bellows a few lines in the original Greek, most of the story is rendered in casual contemporary language that puts both mortals and gods on our own level.
