Had a therapist in the hospital explain it in this hierarchy from most benign to most deadly:

Issue ----- Depressed

Thought ----- Suicidal thought
Suicidal ideation
Suicidal plan

Feeling ----- Suicidal intent (when the patient has a plan
with intent, that is when most
pdocs and T's will insist on
hospitalization)

Behavior ----- Suicidal Act

Therapists and pdocs have to figure out that fine line between thought and behavior, and sometimes they err on the side of caution, but having just buried a dear friend who did not express any of the above to anyone in his life at all, I wish he had told someone his thoughts before they moved into deep feelings and he acted upon them.