Englishfor English speakers
appointment
Noun
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A formal agreement to meet or visit someone (for example, a doctor) at a certain time and place.
I have a doctor's appointment at 3:00 tomorrow.
Let's make an appointment for lunch on Tuesday next week.
clause
Noun
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A clause is a section in a contract or other legal document.
The author's contract contained a clause giving him creative control over the films.
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A clause is a group of words that usually includes a subject and a predicate. In English, the subject usually comes before the predicate.
The last clause in the sentence is hard to understand without knowing some background.