Select refers to carefully choosing one or more things or people from a group, according to preference or some criteria of superiority (select one of the candidates, select a necktie to wear to the event). Cull suggests selection or gathering together of a number of things or people, typically by combing through a large quantity. It is often used in the context of research or curation–he culled the footage from video archives. When using cull, however, keep in mind that cull is one of those odd words, like cleave, that has two nearly opposite meanings: culling also means selection of things you want to eliminate (cull out the duplicates in the database, cull the deer population).

Belief and conviction refer to the acceptance of, or confidence in, the truth or rightness of something. Belief is a kind of knowing based on psychological, ideological, or spiritual certainty rather than objective, proven fact (belief in God, popular belief that garlic repels vampires). Conviction suggests unshakeable, deep, and sincere belief that something is true or right, and often has a moral or religious basis. Like belief, conviction can refer either to a subjective state (speak with great conviction) or to a particular thing that is believed (act on one's convictions). The word tends to have a positive connotation of strength of character and integrity. The commitment entailed by a conviction is illustrated in the idiomatic expression, “to have the courage of one’s convictions,” which is to do what one believes is right.

Productive describes a person or thing whose output, in the form of work, products, or positive consequences, is of a quantity to be valuable or profitable. A productive person accomplishes a lot in a day. Productive soil can generate an ample crop. Prolific suggests production of an exceptional amount, often at a fast pace. It’s most frequently used of creative workers–writers, composers, painters, inventors, directors (a prolific composer, who composed over 1000 works in his lifetime), although it is also applied to production of offspring (prolific apple orchard) and many other cases of profuse generation.