What does the term "common time" refer to in music?

The term "common time" specifically refers to a time signature of 4/4. This is one of the most frequently used time signatures in Western music and is characterized by four beats in each measure with the quarter note receiving one beat. The familiarity and straightforward nature of 4/4 time make it the standard for many musical genres, allowing for a wide range of rhythms and styles.

In the context of the other options, while 3/4 is a time signature commonly associated with waltzes, 2/4 is often used in marches, and 6/8 is a compound time signature that gives a different feel, none of these are termed "common time." The designation of “common time” typically aligns with the 4/4 signature, making it a foundational aspect of rhythm in music education and composition.