This is a much-beloved topic of mine.
There are a suite of ad hoc romanisations of non-Roman alphabets, devised for the ASCII-based internet (and phones). Greeklish is the Greek one. And Greeklish varies widely from practitioner to practitioner, mainly as to whether it’s a transcription (capturing the sounds of letters in Roman characters), or a transliteration (so that the Roman letters can be a bit more remote what an English-speaker would expect).
So a xi would be <ks> in the former, and any of <j, $, 3, c> in the latter—mostly to look like ξ, or in the case of <c> because it’s a leftover character in keyboard mappings.
Πώς θα χρησιμοποιούσες διαφορετική αλφάβητο να γράψεις την πρώτη σου γλώσσα (“How would you use a different alphabet to write your native language”) would end up as:
- Phonetic: Pos tha xrisimopoiouses diaforetiki alfavito na grapsis tin proti sou glossa
- Transliteration: Pws qa xrhsimopoiouses diaforetikh alfabhto na grayeis thn prwth sou glwssa.
Of course, Greeks also do the reverse: write English in phonetic Greek. For example, How would you use a different alphabet to write your native language:
- Χάου γουντ γιου γιουζ ε ντίφερεντ άλφαμπετ του ράιτ γιορ νέιτιβ λάγκουιτζ.
The real fun and games was during the hey-day of Greeklish, when Greeks would write English in phonetic Greek—in Greeklish. So:
- Xaou gount giou giouz e ntiferent alfampet tou rai”t gior nei”tib lagkouitz.
Remember: these are of course Modern Greek pronunciations of the Greek alphabet.