Reporting a Statement (ότι / πως)
To report what someone SAYS, THINKS, or KNOWS as a fact, Greek links the reporting verb to the reported clause with a complementizer - ότι or πως, both English “that”: Λέει ότι είναι κουρασμένος (“He says that he is tired”), Νομίζω πως έρχεται αύριο (“I think that he is coming tomorrow”). ότι and πως are INTERCHANGEABLE - ότι is a touch more neutral/written, πως a touch more colloquial - and both are followed by an ordinary INDICATIVE statement, the same tense you would use saying it directly. Unlike English, Greek NEVER drops the “that”: «Λέει είναι κουρασμένος» is wrong - the complementizer is obligatory.
The rule
To report what someone says, thinks, or knows as a fact, Greek joins the reporting verb to the reported clause with a complementizer - ότι or πως, both English “that”: Λέει ότι είναι κουρασμένος (“He says that he is tired”), Νομίζω πως έρχεται (“I think that he is coming”). ότι and πως are interchangeable (ότι a touch more neutral/written, πως more colloquial) and both are followed by an ordinary indicative clause. Unlike English, Greek never drops the “that” - «Λέει είναι κουρασμένος» is ungrammatical; the complementizer is obligatory. Contrast this with να, which follows modal/wanting verbs rather than reporting ones - see ότι/πως vs να.