Correct spelling


Correct spelling, explanation: double n in connection is necessary, because it comes from joining together Latin words prefix con- and the word nectere (to tie). Two consonants n next to each other gave the result of doubled n. Therefore connection is correct and conection is a misspelling.

Definition of connection:
noun, a state or act of being connected; relationship
The internet connection is really poor quality, it keeps lagging all the time!
Jack and Julie have a special connection. They really are true soulmates.

Incorrect spelling


Incorrect spelling, explanation: this form is incorrect, and the correct one is connection, because the original Latin connexare comes from the prefix con- and the word nectere (to tie), so n was doubled and it remained doubled in English (late 14th-century conneccion). The correct form is thus connection, not conection.