godan ~く verb / intransitive verb / transitive:

• to open; to undo; to unseal; to unpack
• to bloom; to unfold; to spread out
• to open (for business, e.g. in the morning)
• to be wide (gap, etc.); to widen

godan ~く verb / transitive:

• to hold (meeting, etc.); to give; to open
• to found (nation, dynasty, sect, etc.); to open (a new business); to set up; to establish; to start
• to open (ports, borders, etc.)
• to open (an account)
• to open up (new land, path, etc.); to clear; to develop ➜ 拓く
• to open (a file, etc.) - IT term
• to extract (root); to reduce (equation) - Mathematics term
• to cut open (fish) - as 魚を開く - Food term
• to change (kanji into hiragana)

godan ~く verb / intransitive verb:

• to flare (e.g. skirt)
• to slacken (into a poor posture) - as 体が開く, 肩が開く, etc. - Sports term