Are "final decision" and "last decision" interchangeable?

Question

Looking into a dictionary entry for last, I come up with:

1) Final, ultimate, coming after all others of its kind.
2) Most recent, latest, last so far.

Looking up final:

1) last; ultimate
2) Conclusive; decisive

Now I'm wondering what's the difference between final decision and last decision, were one to be strict and pedantic.

My theory:

last decision - ambiguous - may mean "final decision" or "most recent decision in a chain of decisions yet to follow
final decision - not ambiguous - means only "final decision"

Am I correct here or am I somehow mistaken?

Answer 1

It honestly depends on context. If you were to say

"That was my last decision." vs

"That was my final decision."

you are likely to mean two different things, as you describe in your question. However, consider

"This will be my last decision." vs

"This will be my final decision."

In this context the former statement implies the latter, so the meaning of the two phrases is the same, whether you mean final in the sense of "not going to change" or final in the sense of "last in a series".