Correct spelling, explanation: the correct form, opened, is spelled without doubling the last consonant of the base form open. The rule says that when a word contains two syllables, with the last syllable preceded by just one vowel, and the accent of the word falls on the first, not last, syllable, we don’t double the last consonant. Therefore, open will not double the n at the end and the correct spelling of the past simple/past participle form is opened, not openned.

Definition of opened:
1. verb (past form of open), unlock, move door or window from the closed state to one that allows passage; to get access
Jane opened the window because it was a hot day.
2. adjective, not closed, unlocked
Could you leave the door opened, so everyone can see where the lecture is?

Incorrect spelling, explanation: according to the rule, when a two-syllable word has the second syllable preceded by one vowel we double the last consonant when adding any suffix, however, this rule only applies to the accent on the last syllable. In the word open the accent falls on the first syllable, therefore we don’t double the last consonant n, and when creating past simple/past participle form it is spelled opened. This is why openned is the wrong spelling, and the only correct form is opened.

Incorrect spelling

Incorrect spelling

Incorrect spelling

Incorrect spelling