FIVE UNUSUAL WORDS

The answers to the five clues below have something in common which makes them five very unusual words. Can you tell what it is?

1. An eagle's nest
2. Farewell
3. Related to hearing
4. Weird
5. A line of people (east coast term)

HINT:

All the answers are words with a certain letter ratio of four to five.

Answers:

1. Aerie
2. Adieu
3. Audio
4. Eerie
5. Queue

All the words have five letters, four of which are vowels.