The correct spelling is opening. The confusion often arises because adding “-ing” to some verbs requires doubling the final consonant, like “running” from “run.”
Definition of opening noun in Oxford Advanced Learner's Dictionary. Meaning, pronunciation, picture, example sentences, grammar, usage notes, synonyms and more.
An opening is a good opportunity to do something, for example to show people how good you are. Her capabilities were always there; all she needed was an opening to show them.
An opening is an empty space. That opening in the back of your closet might lead to a secret room. A job opening, on the other hand, is an available job that could open you up to an entirely new career.
a formal or official beginning, as of a sport season or a season's sale of goods: the opening of the deer-hunting season; Swimsuits sold well at the summer opening.
"Openning" is an incorrect spelling of the word "opening." "Opening" can refer to a hole or start, like the opening of a door or the beginning of an event. It can also mean an opportunity, such as a job opening. In performances, it's the first part, like the opening scene in a play.