English Vocabulary.

2. the way in which two or more things have an effect on each other.
5. an unpleasant hint or suggestion of something bad.
6. endless (often used hyperbolically).
9. say (something) abruptly, especially as an aside or interruption.
10. crossed intricately together; interwoven.
11. ask questions of (someone, especially a suspect or a prisoner) closely, aggressively, or formally.
13. an electrical device allowing one-way or two-way communication.
15. a person who acts as a link between people in order to try to bring about an agreement or reconciliation; a mediator.
16. impossible to understand or interpret.
17. acting or done quickly and without thought or care.
18. impossible to solve.

1. (of a difficulty or obstacle) impossible to overcome.
3. existing or occurring within a state.
4. situated or done within the walls of a building.
6. curring at irregular intervals; not continuous or steady.
7. not harmful or offensive.
8. make changes in something established, especially by introducing new methods, ideas, or products.
10. existing or taking place within, or administered into, a vein or veins.
12. delay or prevent (someone or something) by obstructing them; hinder.
14. well known for some bad quality or deed.