teacher? or teachers? and course? or courses? Does it matter? and please help me understand why.......

# The dictionary will look something like:
# {'Andrew Chalkley': ['jQuery Basics', 'Node.js Basics'],
#  'Kenneth Love': ['Python Basics', 'Python Collections']}
#
# Each key will be a Teacher and the value will be a list of courses.
#
# Your code goes below here.
def num_teachers(teachers):
    count = 0
    for teacher in teachers:
        count += 1
    return count

def num_courses(teachers):
    total = 0
    for value in teachers.values():
        for course in value:
            total += 1
    return total

def courses(teachers):
    result = []
    for courses in teachers.values():
        result += courses
    return result

def most_courses(teachers):
    max_count = 0
    professors = ""
    for teacher, course_list in teachers.items():
        if len(course_list) > max_count:
            max_count = len(course_list)
            professors = teacher
    return professors

def stats(teachers):
    name_list = []
    for teacher, course in teachers.items():
        name_list.append([teacher, len(course)])
    return name_list