Re: aikido = self-defense??? or self-defense = aikido???
Doubt I understand you, since the very definitions I know of are very different. this might be an issue of language too:
Self-defense is a description of a set of actions, done in order to save self and own close ones from physical harm by an attacker. Many people tend to limit self defense to the very actions taken while fighting against such a threat, others look at a wider scope and would include actions before being attacked (e.g. awareness to developing situation, avoidance, de-escalation), some also include actions just after such an event (medical, legal and similar implications).
Aikido is a martial art, for which you gave some partial description above.
-> You can't learn "Self-defense", you can learn a variety of concepts, ideas and responses to help you defend your-self better given some threat. One such example would be learning a martial art, another would be learning to draw and shoot a gun or pepper spray, whichever you own.
-> A martial act can be the knowledge base for some persons actions in self-defense.
-> One may introduce self to many concepts relevant for self-defense while practicing martial arts.