The qal is the simplest, most basic Hebrew stem. Nearly 70% of verbs are qal. It is translated in the active voice. See more on qal QTL or qal YQTL.
The nifal stem represents simple action in the passive voice (as opposed to the qal which is simple action in the active voice). video or pdf or Gesenius In the QTL, the nifal will have a nun prefix; in the YQTL forms, the nifal is characterized by the nifal triangle.
The Hiphil stem generally expresses causative action in active voice, but it can also express other kinds of verbal action depending on the context and the specific verb. more
The unique nuance of hifil verbs is that they are causative. Under the causative is also included the declarative sense, e.g. הִצְדִּיק to pronounce just. Gesenius §53
the causative use of the hifil;
the inner causative (or “intransitive”) use of the hifil;
the denominative use of the hifil;
the declarative use of the hifil;
other uses of the hifil.
The hofal reflects causative action in the passive voice; see here or this video. Every form in the Hofal can have either a qamets-hatuf or a qibbuts under the first letter (so הָ or הֻ). The translation of the hofal is much the same as the hifil. video
In both QTL and YQTL, verbs in the piel are distinguished by the dagesh in the middle letter. video or pdf In the YQTL, they are also recognized by the sheva under the prefix. וַיְדַבְּרוּ
The Piel stem is typically said to represent intensive action in the active voice (as opposed to the pual which is intensive action in the passive voice); see Gesenius. This is a bit simplistic, however. The following videos correct this:
The Pual stem represents intensive action (the same qualifications apply here as in the piel) in the passive voice; see here. Help in translating the Pual is here.
The Hitpael stem is brother to the piel and usually expresses reciprocal or reflexive action. more
Hitpaels undergo various morphological changes called assimilation and metathesis. More on metahesis here.
reflexive use of the hitpael
indirect reflexive use of the hitpael
reciprocal use of the hitpael
iterative use of the hitpael
estimative use of the hitpael
There a few other forms which are so rare that your time is better spent elsewhere. If you insist, you can use these videos to work through them.
40.01 Introduction to Minor Stems