開く， 空く， 明く， あく
1. to open (e.g. doors)
2. to open (e.g. business, etc.)
3. to be empty
4. to be vacant, to be available, to be free
5. to be open (e.g. neckline, etc.)
6. to have been opened (of one's eyes, mouth, etc.)
7. to come to an end
8. to open (one's eyes, ...
开、(门)开了；敞开(例如领口等)；(眼)睁开；(嘴)张开；有孔洞，形成间隙，（事件之间）有间隔