1
Something that is troubling makes you worried or nervous. Common collocation
2
Useful, serious, or important
3
The fact of not being easy to do or understand
4
Something that someone says or writes officially, or an action done to express an opinion:
5
Something that you plan to do or achieve
6
A detailed study of a subject, especially in order to discover (new) information or reach a (new) understanding
7
Something that is usually or regularly done, often as a habit, tradition, or custom
8
A sentence or phrase used to find out information
9
Something that is important to you, or the fact of being important
10
A formal statement of the rules on which a subject of study is based or of ideas that are suggested to explain a fact or event or, more generally, an opinion or explanation
