Incorrect spelling, explanation: openned is an incorrect form, because, in contrast to numerous words, the term open doesn’t follow the typical rule of doubling the final consonant when attaching a suffix. This rule is generally applicable, but it hinges on the emphasis placed on the final syllable. With opened, the emphasis falls on the o, so there’s no need for the last consonant to be doubled. Hence, the correct spelling is opened, not openned.

Correct spelling, explanation: opened is the correct spelling because, in the context of open, we do not employ a doubled n when attaching a suffix. The established rule dictates that for the final consonant to double, there should be a consonant-vowel-consonant ending, with the stress falling on the ultimate syllable. With opened, the accent is placed on the initial syllable, thus precluding the need to double the last consonant. As a result, opened is the appropriate form, whereas openned is incorrect.

Definition of opened:
verb, past simple tense of open, to have unlock or make access to something previously closed; to emotionally and honestly speak about something personal
The opened book on the table hinted at his recent reading habits.
After their opened discussion, they reached a mutual understanding.
I opened up to her, she is really inspiring.

Incorrect spelling

Incorrect spelling

Incorrect spelling

Incorrect spelling