The National Corpus of Contemporary Welsh project hopes to document 10 million expressions and words of everyday slang and formal Welsh.
The first project of its kind, its aim is to capture Welsh, in all its forms, across generations and regions.
Speakers will be able to add their contribution via a new app.
It is hoped the corpus will further understanding of the many different Welsh dialects and regional variations, and help learners.
"If you are teaching the language, you need to be sure you are teaching the words most learners are likely to hear," explained Steven Morris of Swansea University.
"The corpus helps us understand which phrases and words are used most often."
Welsh regional dialect
fodan - girlfriend. Origin: north Wales
jaman - embarrassment. Origin: Caernarfon
shibwns - spring onions. Origin: south Wales valleys
nisied - handkerchief. Origin: old Glamorgan
ffroes - pancake. Origin: old Glamorgan
siop siafins - shambles. Origin: used across Wales
The project, which has been running for a year and concludes in 2019, also hopes to reflect how Welsh has responded to the digital age.
"People are coming up with new phrases all the time," Mr Morris said.
"It shows us the vitality of the language, in that it is being used in so many different ways."
Singer and BBC 6Music presenter Cerys Matthews said the corpus will be a "rich source of information for creative artists, software developers, translators, learners, teachers, policy makers, and anyone wanting to engage with the complexity, versatility and beauty of real, living, Welsh".
Cardiff University linguist Dr Dawn Knight said: "We want conversations - people sat around the table on a Sunday, having lunch.
"People can download the app and just record themselves."
Academics have made a plea for people to "give their Welsh" as part of the biggest ever corpus - or collection - of the language.