Most of the friends I have spoken with since being hospitalized for suicidal intent have expressed a desire to be supportive without having a clue what I have gone through. Many of them have experienced some degree of depression, but not suicidal thoughts, except perhaps briefly and in passing.

When I was in college I took a suicide prevention training to help peers in the dorm. The said that suicidal thoughts indicate depression, but not necessarily suicidal behavior, and to ask directly if a person has a plan. I've always thought of suicidal thoughts as just passing thoughts now and then and suicidal ideation as more frequent and perhaps more urgent thoughts. Really, the definition doesn't matter as much as knowing what kind of help a peson needs (therapy vs. emergency services). I believe follow up with anyone who has any kind of suicidal thoughts is critical because thoughts can progress to plans very quickly (in my experience). They're a red flag vs. a normal occurance.

I really like what Deli has to say in this thread.