Correct spelling, explanation: open entered English from the Germanic language in the times of Old English. Already then it had the form open, but also version openian functioned. The meaning of the word hasn’t changed much and today open is a commonly used verb and adjective.

Definition of open:
1. adjective – refers to something which is not closed, to an honest behavior, or to available options;
There’s somebody at the door so I will open it.
Don’t be afraid to be open about your problems – you can tell me everything.
Once you finish this university, the job market will be open to you.
2. verb – to start something, the opposite to close something;
The mayor of the city will open the marathon with a short speech.
I can’t wait to open the box that’s waiting for me at home.

Idioms with open:
A few interesting idioms include:
1. open somebody’s eyes – when somebody starts to realize something shocking;
I had to open his eyes and tell him that his wife is cheating on him.
2. welcome somebody with open arms – to be happy to see someone;
We haven’t seen each other for ages so they welcomed me with open arms.
in the open – when something is no longer a secret;
Now when he showed his feelings out in the open, I don’t know what to do.

Incorrect spelling, explanation: open is not a complicated word when it comes to both pronunciation and spelling, but it is sometimes troublesome as a popular mistake is to write the word open as oppen. It is wrong, though, as open features only a single p letter.