The paramis or paramitas are the perfections cultivated on the way to awakening, and the two great branches of Buddhism enumerate them differently, a difference that reflects what each expects of a practitioner rather than a mere disagreement about arithmetic.
The Theravada ten: generosity (dana), moral conduct (sila), renunciation (nekkhamma), wisdom (panna), energy (viriya), patience (khanti), truthfulness (sacca), determination (adhitthana), loving-kindness (metta) and equanimity (upekkha). This list belongs chiefly to the Buddhavamsa and the Jataka literature, where it describes the career of a bodhisatta across countless lives before Buddhahood, with individual Jataka stories illustrating individual perfections, the tale of Vessantara for giving, of the patient ascetic for forbearance. In Theravada the perfections are therefore associated primarily with the exceptional path to Buddhahood rather than with the ordinary path to arahantship, though later and modern Theravada practice has drawn on them more broadly as a framework of virtue.
The Mahayana six: generosity, moral conduct, patience, energy, meditation (dhyana) and wisdom (prajna). This is the standard set and it is universal in Mahayana literature. Wisdom is given a distinctive controlling status: the Perfection of Wisdom sutras hold that the other five become perfections only when informed by prajna and the understanding of emptiness. Generosity is perfected when giver, gift and recipient are all seen as empty of inherent existence, the "threefold purity", so that the practice is not a transaction generating merit for a self. A later expansion adds four more to make ten: skilful means (upaya), aspiration (pranidhana), power (bala) and knowledge (jnana), aligning the perfections with the ten bodhisattva stages of the Dasabhumika Sutra.
The difference between the two lists is not merely one of length. In Mahayana the perfections are for everyone, because the bodhisattva path is held out as the path for all practitioners rather than for a rare few, and they are practised for the sake of all beings rather than for one's own release. In Theravada they describe a voluntary and extraordinary career undertaken by a very small number.
Both traditions place generosity first, and both give the same reasons for it: that it is the most accessible of the practices, that it works directly against grasping, and that it establishes the disposition on which everything else is built.