οτι has the following uses (see GGBB page 748 or any of the lexicons):
A content οτι
In this use, οτι introduces the content of what is said, thought, perceived, remembered, known, sworn, etc.
Direct discourse
Here the οτι is introducing direct discourse and can be translated with a set of quotation marks.
Apposition
Here the οτι introduces a word, phrase, or clause that is in apposition to some other noun.
Causal
In this usage, the οτι is a DMW for an adverbial, dependent clause showing cause.
