Pali term for awakened being, corresponding to the Sanskrit word bodhisattva.
While Mahayana Buddhism uses the term bodhisattva, Theravada prefers bodhisatta.
More than a lingustic preference, there is a difference of emphasis or even understanding of the term. Since there already are several nodes on the Mahayana bodhisattva ideal, I will briefly describe the Theravada understanding here.
The Pali scriptures use the term bodhisatta whenever they talk about the previous lives of the Buddha. In a way, the term bodhisatta describes a "Buddha in training".
Theravada Buddhism makes a clear distinction between a Buddha and an arahant: A Buddha is one who obtains Nibbana (which is what Pali calls Nirvana) entirely on his own, while an arahant obtains it with the help of a Buddha. The end result is exactly the same: Nibbana, awakening, end of suffering, freedom from samsara.
The difference can be likened to the doctor and the patient afflicted with the same disease, particularly a disease for which there is no known cure.
The bodhisatta then is a being determined to find the cure even if it requires hard work, countless experiments and failures, effort spanning through many a lifetime.
Once he has found the cure, the bodhisatta cures himself and thus becomes the Buddha (or the "doctor").
Of course, once the cure is known, it is not necessary for everyone else to find it. The doctor can prescribe the cure for anyone else afflicted by the same disease (the "patient"). The being who follows the advice of the Buddha will be equally cured, in our case will obtain Nibbana through the help of the Buddha. The patient thus cured is the arahant.
While most Mahayana Buddhists follow the bodhisattva ideal, most Theravadins do not. Their reasoning is, why go through all the trouble of reinventing the wheel (no pun intended - wheel being the symbol of Buddhism)? That is not to say that an individual Theravadin may never choose the bodhisatta path, only that most of them do not.
Theravadins generally point out that only so many doctors are needed to cure a large number of patients. They certainly do not object to anyone wishing to become a Buddha: After all, doctors are needed, they simply say it is not necessary for everyone to become one. Whether one chooses the path of the bodhisatta or that of the arahant is a matter of personal preference, just as some people decide to become doctors, others choose a different path, and go to the doctor when they are sick. Neither choice is "better", they are just different.
Both, Theravada and Mahayana Buddhism have a great respect for the bodhisattas/bodhisattvas.