The answer is B. Semicolon.
A seminar is a meeting of people to discuss a particular topic. A semicolon is a punctuation mark used to separate two independent clauses. A semifinal is a match played between the two teams that have won their respective matches in the first round of a competition. A semicircle is a half-circle. A semitone is a musical interval that is half the size of a whole tone.
Semicolons are used to separate two independent clauses that are closely related in thought. They are also used to separate items in a list that already contains commas.
Semifinals are usually played in a best-of-three format, meaning that the first team to win two matches wins the semifinal.
Semicircles are often used in architecture and engineering. They can also be found in nature, such as in the shape of a rainbow.
Semitones are the smallest interval in Western music. They are used to create scales and melodies.
In the given options, all are related to the concept of “half” except semicolon.