There are wrong words you could use in the viva. You could exaggerate or bluff. You could lie! You could mis-speak. You could be too modest or you could be careless in your thought or speech.
There are no perfect words for the viva discussion. Your examiners don’t expect you to respond like a machine without hesitation, errors or deliberation. Questions can have answers but they could also have opinions offered or hunches shared. You can say I don’t know.
You need the right words in your viva. The right words aren’t perfect, but they are considered. The right words aren’t scripted but can benefit from practice beforehand. The right words don’t require knowing the questions ahead of time or special understanding of the process.
The right words just require you to do the work. Do the work and you’ll find the right words on your viva day.