The analysis is built downward from three roots. Lobha is greed, the mind reaching toward what it wants. Dosa is hatred, the same mind pushing away what it does not want. Moha is delusion, the not-seeing that lets the other two operate unchallenged. These are the akusala-mula, the unwholesome roots, and every unwholesome act is traced back to one of them. Their absence is not treated as a neutral state but is itself named, as the wholesome root, which is a small point with large consequences: the tradition holds that the ordinary condition to be cultivated is the absence of the three rather than the presence of an opposing virtue.
Later usage, and Mahayana usage in particular, calls the three poisons, and pictures them at the hub of the wheel of becoming as a cock, a snake and a pig, each biting the tail of the one in front. The image places them at the centre of the whole diagram of rebirth, which is exactly the claim being made about them.
From the roots come ten courses of unwholesome action: three of body, killing, taking what is not given and sexual misconduct; four of speech, false speech, divisive speech, harsh speech and idle talk; and three of mind, covetousness, ill will and wrong view. That the last three are mental states rather than deeds is the point of the enumeration. Intention is where the act is located.
The comparison with the Western seven is instructive precisely where it fails. Greed and hatred have obvious counterparts among the capital sins. Delusion has none at all, and it is the root the Buddhist analysis treats as the deepest of the three.