How do you know he has lost interest in you?

The question above. Ghosting is the most obvious sign, but let's put that he doesn't do it, he hasn't blocked you yet, and he can answer you if you contact him first, but the point is to give him the chance of contacting you before you do it (and asking him why he hasn't). So how long do you need to wait for him to take the initiative in contacting you?
How do you know he has lost interest in you?
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