1. Not everyone learns at the same pace.
2. Something at home might of come up, loss of someone or sickness.
3. To give the chance to pass.
The New Oxford American Dictionary (NOAD) is a substantial revision of the Oxford Dictionary of English (ODE, which is a British English dictionary). ... ODE was revised for NOAD, with some spelling changes, new words found only in the US, and (rarely) some changes in the order of entries for the American market.
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