All that's left of the Gamilaraay language from northern NSW and southern Queensland are a few phrases spoken by fewer than 50 people.
"The language stopped changing 70 or 80 years ago," said John Giacon, a lecturer at the Australian National University who is trying to bring the language back from the brink of extinction.
"Many of the things we want to talk about today, there are no words for them.
"There are 60 hours of tapes [in the language] where they're talking about hunting kangaroos, there's no way you could practice with that."
Dr Giacon and his team have been working with Aboriginal communities to develop a dictionary that now has about 2500 words, and is being used to teach an intensive summer course on the language run by the ANU, one of a few of its kind at the tertiary level.
Kevin Lowe, who is a former inspector of Aboriginal education for the NSW Board of Studies (now the NSW Education Standards Authority), said that figuring out how to translate simple phrases to Gamilaraay can take months.
"We wanted to talk to a class about boys getting on their bikes and going fishing, which is a simple idea and easy to say in English," Dr Lowe said.
"So we emailed John [Giacon] and said 'how would you say this?' He came back two months later and said, this is my best effort by going back to the tapes and looking at what we know."
Words such as mobile phone or computer need to be constructed from words that already exist in Gamilaraay or a close dialect, Yuwaalaraay.
???"The main things you need for language teaching are fluency, resources and infrastructure for learning," Dr Lowe said.
"For most NSW languages, the resources we've got are all gone and it's hard to find fluent speakers in any of these places because they haven't had the opportunity to learn it or speak it.
"Kids in schools speak Japanese or French or German because that's what they have access to."
Garruu Victor Chapman, from Hebel in southern Queensland, said he spoke the language as a young boy but was punished for speaking it at school.
"They used the cane for speaking your language, it's a very effective way of knocking it out of you," he said.
"My parents spoke it but they were hesitant to pass it on because they were conscious of the fact that you were penalised for speaking your language."
Priscilla Strasek, from Lightning Ridge in northern NSW, is doing the intensive Gamilaraay course as part of a bachelor of education from Charles Sturt University.
Ms Strasek said her grandparents spoke the language and she now wants to see it revived for her own children.
"A language is your connection to your culture and your mob," she said.
"To be able to do it at uni is a really big change in 20 years."
Sophia Brown, who lives in Tamworth and is also doing the summer course, said that language is a big part of developing a shared identity.
"If you say 'Yaama' ['hello' in Gamilaraay] in a sentence, you'll be surprised at who'll turn around and say, 'I recognise that word', and the next question is always, 'Where are you from?'"
For Tracy Cameron, a tutor at the University of Sydney, learning the language is "a responsibility".
"There's a worldwide movement to revitalise languages, we can look to the Maori language, Indigenous languages in Canada, Welsh, Gaelic," said Ms Cameron, who is learning Gamilaraay with her son Angus, a communication student at the University of Technology Sydney.
"We're part of that movement."
The summer course is being held at Charles Darwin University's Sydney campus. The university also plans to establish the Australian Indigenous Languages Institute and begin offering courses in other languages such as Yolngu Matha in January 2019.