Trill initiates are those of the Trill species who join an initiate program in order to train themselves for potential joining with a symbiont. The initiate program consists of an intense series of exams and evaluations, both mental and physical, that are designed to eliminate all but the most suitable and dedicated applicants. Over five thousand candidates qualify for the training each year. On average, only three hundred symbionts, annually, are available. As such, it does not take much for an initiate to be knocked out of consideration. Only the best and brightest are joined.
Initiates are first evaluated by the Trill Symbiosis Commission, which is responsible for their training. Near the end of the program the initiates are assigned to a field docent, a joined Trill who evaluates their suitability in real-world environments.
Curzon Dax was known to be a particularly harsh field docent and personally eliminated many candidates, including Jadzia. Jadzia went on to become the only initiate ever to be rejected and then later re-accepted for the program. The experience made her determined to be a different type of docent for initiates when she was charged with evaluating Arjin during his initiate period.
The strenuous nature of the evaluation can be intimidating for many initiates, and rejection often led to deep disappointment and loss of purpose. Verad serves as a striking example. After his rejection from the program, which he believed was unwarranted, he was determined to capture a symbiont from a current host and join with it outside the strictures of the Symbiosis Commission. To this end he removed the Dax symbiont from Jadzia Dax and was briefly joined with it in 2370.