Quick, what's the definition of a ballad? If you hesitated, don't worry, like the old adage about not being able to define pornography, but knowing it when you saw it, defining a ballad can be tricky. Some call it a slow jam that soothes your mind, others refer to it as a song without heavy bass, noted primarily for the longing and heartache in the lyrics. One of Merriam-Webster's dictionary of a ballad, references slow, romantic or sentimental songs, but another defines it as a long, narrative composition in verse that can also be sung. As a means of clarifying the definition of a ballad, here are few examples that might help.
Sentimentality. Probably the most well-known definition of a ballad is the sentimental or sad song, popular in Victorian times, that evokes lost love or great memories of past days. Examples would include the famous 1913 ballad "Danny Boy," a recognized classic about a boy going off to war.
Pop. Another type of ballad is the modern or pop music ballad, where the emphasis is on emotional lyrics, plaintive singing and a distinct lack of heavy guitars or other instruments that might disrupt the quiet ambience. Great examples include the Eagles "Hotel California," an epic ballad about a hotel that's a metaphor for Hell, and Billy Joel's "Piano Man," a song of lament about the patrons of a bar who seek comfort from their daily travails by listening to the piano player.
Power. Born from the hard-rock era of the 1970's, power ballads became a way for heavy-metal bands and artists to show a softer, more gentle side, while still maintaining street credibility with soaring synthesizers, electric guitars and backing choirs. Some of the greatest rock bands are known for their signature power ballads, including Led Zeppelin with "Stairway To Heaven," Aerosmith with "Dream On" and Guns N' Roses with "November Rain," a nine minute opus that became the longest song ever to reach the top ten on the Billboard charts.
As you can see, there's no right or wrong answer when asked to define a ballad, you know one when you hear it. However, a familiarity with the different kinds of ballads that have been popularized in music can help give you a greater sense of confidence the next time that slow song plays on the radio, and you start explaining to your friend the different ways to define the song as a ballad.