英和和英

reeve an opening

The door has opened

The door is open.

the opening salvo

a splayed opening

the opening act

The curtain rises

The plays begins

The performance commences.

cut open

evolution and involution

to extract the square root （of a number）

to open (something) completely

to open again after closing

to make a beginning―pave the way for something

to pave the way for something

The door is open.

to open completely

open

a complete phrase

to unseal

being completely open

an unsealed letter

open formally

opening a mine

termination of operations

to wad the openings

to break the seal―（みだりに開封するの意味なら）―tamper with the seal

split open

to open up