Observation

mishkamu	s/he finds it	nimishken	I find it
shashkaimu	s/he lights it	nishashkain	I light it
pakuneimu	s/he pierces it	nipakunein	I pierce it

The stem of TI verbs like mishkam^u is the part mishk- that comes before the endings -am^u or -en. The stems of verbs like shashkaim^u and pakuneim^u are shashkai- and pakunei- (before the endings -m^u or -n).

There are 2 types of TI stems:

• Stems ending in a consonant (dictionary form ends in -am^u): mishkam^u
• Stems ending in ai or ei (dictionary form ends in -aim^u or -eim^u): shashkaim^u, pakuneim^u

HISTORICAL NOTE
Historically, all TI verbs were conjugated the same way. ai and ei stem TI verbs ended with an h, which was preserved in the Mashteuiatsh dialect: tashkahamu s/he splits it, ashtuehamu s/he extinguishes it, which became tashkaimu and ashtueimu in the other dialects.

SPELLING CHALLENGE
It’s not easy to dintinguish -ai- verbs (like tashkaimu s/he splits it) from -ei- verbs (like pakuneimu s/he pierces it), because -ai- and -ei- tend to be pronounced the same way: [e:j] or [i:], [ta∫ke:jm] or [ta∫ki:m]. Spelling these TI verbs correctly requires effort, and we recommend using the dictionary when in doubt.