The words வா ("come") and போ are called irregular because they do not follow all of our previously learned rules exactly. The easiest way to show which rules these verbs follow is through a chart.
|present tense||வரு + கிற் + verb suffix||போ + கிற் + verb suffix|
|future tense||வரு + வ் + verb suffix||போ + வ் + verb suffix|
|neg. command (non-resp.)||வராதே||போகாதே|
|neg. command (resp.)||வராதீர்கள்||போகாதீர்கள்|
Take a close look at the commands with respect, since they are much different from all the other verb forms. These aren't the only irregular verbs, but forunately, there are only a few others.