In both prefix and affix forms, verbs in the piel are distinguished by the dagesh in the middle letter. See more here or this video.
וַיְדַבְּרוּ
In the prefix form, they are also recognized by the sheva under the prefix.
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). This can be misleading, however. The videos below go into much more detail on this.
“The fundamental idea of Piel, to which all the various shades of meaning in this conjugation may be referred, is to busy oneself eagerly with the action indicated by the stem. This intensifying of the idea of the stem, which is outwardly expressed by the strengthening of the second radical, appears in individual cases as
(a) a strengthening and repetition of the action;
(b) a causative sense (like Hifil);
(c) Denominatives are frequently formed in this conjugation.” video (source)
- The factitive use of the piel
- The denominative use of the piel
- The pluralizing use of the piel
- The declarative use of the piel
