Five words have been given, out of which four are alike in some manner and one is different.
Select the odd one.

Semicircle, Semicolon, Semifinal, Seminar, Semitone

Given: Semicircle, Semicolon, Semifinal, Seminar, Semitone

Logic: Semicircle, Semicolon, Semifinal, and Semitone all contain the prefix "Semi-", which means half or partial.

Seminar (Does not contain the "semi-" prefix in the same sense; it means a meeting or discussion session)​​

So, Seminar is the odd one out.

Thus, the correct answer is (c).