On grammatical class:

pe'a
marks a construct as figurative (non-literal/metaphorical) speech/text.
pe'ainai
technical meaning; marks a construct as jargon/terminology/technical/precise/exact speech/text
pe'anai
literal sense; marks a construct as literal (non-figurative/non-metaphorical/exact) speech/text
pe'ai
discursive: layperson/laïc meaning; marks a construct as layperson/common/non-technical/non-jargon speech/text