These terms are often used inter-changeably. If you become proficient or competent in multiplication of numbers 1-10, you are saying that you are able to perform the task of multiplication, and likely with accuracy and little to no struggle. You could also say that you have mastered your multiplication tables 1-10.
However, these words can also be used to describe different levels. In these cases, proficiency is typically a level where one is able to perform a task or understand something, but perhaps with some struggle or room for improvement. To become competent is a step above that, and to achieve mastery is to reach a level of perfection. Note that “level of” perfection might mean something equivalent to 80%, not necessarily 100%, depending on the context.
The words can also be mixed within the same sentence, again meaning about the same thing. We could say that a student has mastered the list of competencies and has therefore demonstrated proficiency in the subject area.
A list of competencies is not necessarily a list of standards, although it could be. It could also be key skills or knowledge that the student identifies as necessary for his or her goals, and these may or may not be something you would see on a list of state or national standards.
When we say “competency-based” or “proficiency-based”, we are not saying “standards-based.” The standards are just one place that you look for a list of learning goals; they may or may not be relevant for the student’s plan or the school’s design. Instead we are saying that a course that is competency-based will have a list of learning goals that the student must master in order to successfully complete the course.
These words are often used to refer to specific, smaller skills, but one can apply the terminology to Big Ideas too. A person mastering the craft of creative writing is really demonstrating mastery of many smaller competencies that are part of the writing process – both cognitive and affective.
How, then, do you know what is meant when these words are used? Context. Who is saying them, and in what scenario or context? For CMASAS as an example, “mastery” means 80% or higher (preferably higher); competencies are learning goals of any kind whatsoever; and a class that is competency- or proficiency-based is a class where students aim to demonstrate mastery for each learning goal. Learning goals can range from smaller, micro-goals to Big Ideas, and they can be from a pre-designed class or goals that students set for themselves.