-ku Godan/u-verb

1. to open; to undo; to unseal; to unpack
2. to bloom; to unfold; to spread out
3. to open (for business, e.g. in the morning)
4. to be wide (gap, etc.); to widen
5. to hold (meeting, party, etc.); to give; to open
6. to found (nation, dynasty, sect, etc.); to open (a new business); to set up; to establish; to start
7. to open (ports, borders, etc.)
8. to open (an account)
9. to open up (new land, path, etc.); to clear; to develop
10. computing to open (a file, etc.)
11. mathematics to extract (root); to reduce (equation)
12. food to cut open (fish) (as 魚を開く)
13. to change (kanji into hiragana)
14. to flare (e.g. skirt)
15. sports to slacken (into a poor posture) (as 体が開く, 肩が開く, etc.)
16. Go usually kana to extend (usu. ヒラく)

-ku Godan/u-verb

1. to open (e.g. doors) (esp. 開く)
2. to open (e.g. business, etc.) (esp. 開く)
3. to be empty (esp. 空く)
4. to be vacant; to be available; to be free (esp. 空く)
5. to be open (e.g. neckline, etc.) (esp. 明く)
6. to have been opened (of one's eyes, mouth, etc.) (esp. 明く)
7. to come to an end (esp. 明く)
8. to open (one's eyes, mouth, etc.) (esp. 明く)
9. to have a hole; to form a gap; to have an interval (between events)