Is this condition necessary, sufficient or neither?
A necessary condition must be present, while a sufficient condition is enough to produce the result under the stated rules. Scoring at least 40 is necessary for a course that also requires attendance. The score alone is not sufficient if a student can still fail because the attendance requirement is unmet.
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Required does not mean enough
Consider a fictional course with two passing requirements: a score of at least 40 and attendance of at least 75%.
A score of 40 or more is necessary because nobody can pass without it. But it is not sufficient because attendance must also qualify.
Meeting both conditions is sufficient under these stated rules, assuming there are no additional requirements.
Confusing the two can weaken everyday explanations. A working internet connection may be required for an online meeting, but it does not guarantee that the microphone, invitation and meeting service work. When someone says a result needs X, ask whether X merely removes one obstacle or actually completes all the conditions for the result.