What is vexatious action and what is an abuse of process?

What little distinction exists between a vexatious action and one that is an abuse of process is often not clear as the two concepts have strikingly similar features. Macaulay J. noted this in Freshway Specialty Foods v. Map Produce LLC, et al., 2005 BCSC 1485, at para. 52:

There is no bright line dividing a vexatious proceeding from one that is an abuse of the court’s process. In my view, the factors that signal a vexatious proceeding also signals an abusive process. Abuse of process is a wide concept however and may extend beyond vexatious proceedings to capture any circumstance in which the court’s process is used for an improper purpose. As pointed out by Baker J. in Babavic v. Babowech, [1993] B.C.J. No. 1802 (S.C.), a decision not referred to by counsel, the categories of abuse of process remain open and include, for example, “proceedings which are without foundation or serve no useful purpose and multiple or successive proceeding which cause or are likely to cause vexation or oppression” (para. 18). Discussion Preliminary Matter: The Settlement Agreement