Types of check valves. A ball check valve is a check valve in which the closing member, the movable part to block the flow, is a spherical ball. In some ball check valves, the ball is spring-loaded to help keep it shut.
(October 2016) Learning is the act of acquiring new, or modifying and reinforcing existing, knowledge, behaviors, skills, values, or preferences which may lead to a potential change in synthesizing information, depth of the knowledge, attitude or behavior relative to the type and range of experience.
The definition of a lesson is something that is to be learned, a learning period or a plan for teaching. An example of a lesson is an English teacher's plan for her next class. Lesson is defined as to teach, instruct or discipline.