hetu: 'cause', condition, reason; (Abhidhamma) root-condition.
In Sutta usage it is almost synonymous with paccaya, 'condition', and often occurs together with it ('What is the cause, what is the condition', ko hetu ko paccayo (Uparipaṇṇāsa-aṭṭhakathā).
In Abhidhamma, it denotes the wholesome and unwholesome roots (mūla, q.v.).
In that sense, as 'root-condition' (hetu-paccaya; s. paccaya), it is the first of the 24 conditions given in the introduction to the Paṭṭhāna (s. Guide, p. 117).
The Dhs (1052-1082) and Paṭṭhāna (Duka-paṭṭhāna; Guide, p. 144) have sections on roots (hetu). -
The term is also used (a) for the classification of consciousness, as sa-hetuka and a-hetuka, with and without concomitant root-conditions;
(b) for a division of rebirth consciousness into ahetuka, dvihetuka and tihetuka, without, with 2, or with 3 root-conditions (s. paṭisandhi).