To Open
To Be Open
intransitive verb, godan verb
あく
開く （あく） To Open, To Be Open
空く （あく） To Become Empty, To Become Vacant, To Become Available
空く （すく） To Become Less Crowded, To Get Empty, To Be Hungry
開ける （あける） To Open Something
ひらく is both Transitive and Intransitive and is often used for the more abstract meaning of open, e.g. to open a meeting.