A true necessary condition in a conditional statement makes the statement true (see  truth table  immediately below). In formal terms, a consequent N is a necessary condition for an antecedent S, in the conditional statement,  N if S ,  N is implied by S , or N S. In common words, we would also say . N is weaker than S  or  S cannot occur without N . For example, it is necessary to be Named, to be called Socrates. A true sufficient condition in a conditional statement ties the statement's truth to its consequent. In formal terms, an antecedent S is a sufficient condition for a consequent N, in the conditional statement, if S, then N ,  S implies N , or S N.
The Heart of Teaching: What It Means to Be a Great Teacher. What does it mean to be a great teacher? Of course credentials, knowledge, critical thinking, and all other faculties of intelligence are important. However, a great teacher should be much more than credentials, experience and intelligence.
Teachers can be popular just because they are friendly and helpful, but to be truly professional and effective they need other qualities. Students may not be able to put their finger on just why one teacher is more effective than another but we need to be able to identify the skills and behavior we require in a true professional. A professional teacher needs to be confident without being arrogant. Nobody can expect to have all the answers, so if a student asks a real stinker, the professional teacher should be able to admit defeat but offer to find out more for the student. And they must carry that promise out. Proper preparation is another crucial requirement of professionalism.