Description:

'CO' is the Common abbreviation for 'na cenukéulkas orkanysyn', the proper term for 'genetically modifier organism', which we in Britain still call a 'GMO' (although English speakers in the Order just say 'CO').

The general public tends to use it imprecisely. 'Na CO' could refer to a specific GMO or genetic modification in general. You will see COs used for the sense of 'genetically modified'.

As is not unusual for casual writing in Common, where people don't always realise the word they're using is an acronym, you will sometimes see written out forms like ce-o and ce-os, with or without the hyphen to convey the difference with 'ceo', which has clear stress on the first syllable as opposed to more equal stress in CO. However, this way of writing it is not correct.