An eighth note is a musical note that lasts for half the duration of a quarter note. It is represented by a filled-in oval note head with a stem and one flag. In a 4/4 time signature, there are eight eighth notes in a measure, allowing for a quick and rhythmic flow in music. Eighth notes can be combined to create various rhythms and are often used in different musical styles, from classical to pop. When two or more eighth notes are connected by a beam, they are played in a smooth, connected manner, enhancing the overall musical expression.