Trotting out brief dictionary definitions is rarely useful for precisely nailing down the common meaning of words, as it is hard to express nuance in such a sma

Trotting out brief dictionary definitions is rarely useful for precisely nailing down the common meaning of words, as it is hard to express nuance in such a small space. Fortunately, though, Oxford actually does go out of its way to make it clear. Unfortunately, you omitted those extra details. Let's look at the bullet points clarifying the meaning: "indicating a desirable or expected state" "used to give … advice or suggestions" One of the examples it gives is, "by now pupils should be able to read with a large degree of independence." Few native English-speakers would read that sentence as saying that there is no option but for students to read with a large degree of independence. What it means is that such a level of reading is desirable or expected, but not required. In common usage, should is much weaker than must. Another good example: "I should exercise tonight" vs. "I must exercise tonight." The former almost sounds like the speaker knows it won't happen and feels guilty, whereas the latter sounds like the speaker is bound and determined to exercise. Don't you think?