Karma and Sanskara seam to be very much related. How are they related and how are they different.
It seems that sanskaras are the precursors that lead to karma http://en.wikipedia.org/wiki/Sanskara "In Hinduism sanskaras or samskaras (Sanskrit संस्कार meaning impression; under the impulse of previous impressions) are the imprints left on the subconscious mind by experience in this or previous lives, which then color all of life, one's nature, responses, states of mind, etc. The Dictionary of Common Sanskrit Spiritual Words says, "Whenever an action is performed with the desire for a specific result (whether for oneself or another), sanskara is created for that person. These accumulate and determine the situations with which we will be presented in the future and will influence the scope of future actions.""
Sanskaras are impressions derived from past experiences that form desires and fears that influence future responses and behavior (karma).
So it seems by being attached to the outcome of an action that karma results. Is that not something we can all agree on?
Saṅkhāra refer to all conditioned phenomena. That means everything else apart from Nibbana. Karma refers to volitional acts which is only a subset of Saṅkhāra. All Saṅkhāras come under the first noble truth, i.e. Dukkha. All Saṅkhāras are impermanent. All Saṅkhāras are non-self.
I have translated (awk-word-ly) sankhara as 'own-making'. SAN = one, once, with, own, con, com; khara = make. This is not without precedence in that 'I-making' and 'my-making' are also found in the Pali, but it is not well accepted as of yet. It is kamma from the point of view of personalization. The making of one's own world. The definition is helpful:
Sankhara is identification with the intent to create personal experience through acts of thought, word and deed, and the identified with consequence. By pushing out the deed a marker of sorts is attached to the consequences which results in the experience "my---".
Like kamma, it is two sided: the doing and the result. In translations the danger for the reader is that it is almost always translated one-sidedly. 'Activities' or 'Fabrications' or 'Volitional activities' and then when dealing with the consequences an unrelated word is used: 'constructed', 'conditioned'.
You might find this discussion interesting: http://obo.genaud.net/dhammatalk/dhammatalk_forum/dhamma_talk/dt_009.conditioned.vs.own-made.htm
Saṇkhāra-paṭiccasamuppāda (kamma-bhava, karma) means it causes, conditions, becoming (jāti, upatti-bhava, 5 khandha).
Saṇkhata (5 aggregate-effects) means it is caused, is conditioned, by 5 aggregate-causes.
Saṇkhāra (5 aggregate-causes) means it causes, conditions, 5 aggregate-effects.
Asaṇkhata (nibbāna) means it is unconditioned by any saṇkhāra.
So, paṭiccasamuppāda is called vaṭṭa, never ending cycle, because it is a loop of aggregates causes and effects. For explanation: ignored, attached, and clinged aggregates had done the past kamma, saṇkhāra-paṭiccasamuppāda, to get the present effected aggregates, then ignoring, attaching, and clinging aggregates do the present kamma, kammabhava-paṭiccasamuppāda, again, to get the future effected aggregates, jāti of Ignored, attached, and clinged aggregates, suffering. Therefore, paṭiccasamuppāda is never ending loop cycle of aggregates, suffering.
When the practitioner contemplating paṭiccasamuppāda, 3 characters will gradually clearly appear to him. Then he can do high level insight meditation, 3 characterizes contemplating.
You can see these pali-words everywhere in canon. This is the reason that why I often told everyone to recite and memorize pali canon.