The words th ("come") and Ngh 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.
| irregular verbs | ||
| verb form | come | go |
| verb root | th | Ngh |
| present tense | tU + fpw; + verb suffix | Ngh + fpw; + verb suffix |
| future tense | tU + t; + verb suffix | Ngh + t; + verb suffix |
| command (non-resp.) | th | Ngh |
| command (resp.) | thUq;fs; | Nghq;fs; |
| neg. command (non-resp.) | tuhNj | NghfhNj |
| neg. command (resp.) | tuhjPu;fs; | NghfhjPu;fs; |
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.