Two articles that are relatively short and to the point that address the question of what particular crimes are implicated by what we currently know re: the Trump campaign and Russia.

Donald Trump Jr. May Well Have Committed a Federal Crime, Experts Say

If Donald Trump is a Crook, What Kind is He?

I believe the second article speaks to OO's complaint about the definition of "collusion." The explanation offered in the article mirrors my own understanding/assumptions of how the word was being (colloquially) used.

Neither article addresses the question of whether Trump attempted to obstruct justice in his interactions with Comey or others. There are articles on that subject, too, of course.

One final note: the possible crimes discussed in these articles are based on the facts as currently known or suspected. Facts lead to whether, and what, crimes may have been committed. Contrary to OO's murder example, you don't always start out with knowing what crime you're investigating first. You probably have an inkling--which is why you're investigating in the first place--but you don't have your conclusions yet. It's not always like murder where there is a dead body with a gunshot in the chest--in those situations, you know a crime has been committed, and you're just trying to find out who did it and how. To rely on this model to argue that this is all a witch hunt because there's no proverbial dead body here is fundamentally flawed. Sometimes the investigation is about *whether* a crime has been committed.