25 Most Common Conjunctions

1. and
2. that
3. but
4. or
5. as
6. if
7. when
8. than
9. because
10. while
11. where
12. after
13. so
14. though
15. since
16. until
17. whether
18. before
19. although
20. nor
21. like
22. once
23. unless
24. now
25. except

Adapted from: http://www.wordfrequency.info