What is the difference between 首相 and 総理?


I learned `総{そう}理{り}` as the word for Prime Minister, but I've recently
learned that `首{しゅ}相{しょう}` is also used. Is there a difference in usage or
meaning? Is one more polite than the other?




総理 is an abbreviation for 総理大臣, which in turn is an abbreviation for 内閣総理大臣.
This is specifically the Prime Minister of the Cabinet (内閣) and is a formal
title.

首相 is the common and informal name. In Japan, this refers to 内閣総理大臣.
Originally, a 相 is a person who assisted a lord or emperor in his work. This
is essentially a minister. The primary or head 相 is known as 首相, which in
Japan is the Prime Minister. Note that one of the meanings of 相 is "to help",
which leads to the above usage.




総理 is an abbreviation for 総理大臣, which in turn is an abbreviation for 内閣総理大臣.
This is specifically the Prime Minister of the Cabinet (内閣) and is a formal
title.

首相 is the common and informal name. In Japan, this refers to 内閣総理大臣.
Originally, a 相 is a person who assisted a lord or emperor in his work. This
is essentially a minister. The primary or head 相 is known as 首相, which in
Japan is the Prime Minister. Note that one of the meanings of 相 is "to help",
which leads to the above usage.

