Looking at the comments on the (mainly classical) pieces recorded on my YouTube channel, I am struck by how common it is for young musicians to refer to every piece they play as a ' song '. A common comment I get is 'I'm learning this song', and a teenage violinist called me the other week to ask if she could rehearse with me some 'songs' she was learning (they were all classical pieces). This is a very recent linguistic development, and probably stems from marketing blurb for digital downloads. For example, the iTunes website has the following: "The music you love (and have yet to discover) is just a click away. You’ll find millions of high-quality, DRM-free songs on the iTunes Store all for just 69¢..." (my emphasis)
So, for many, music = songs. Perhaps the late Henryk Górecki saw this coming when in 1976 he subtitled his 3rd symphony 'Symphony of Sorrowful Songs'! There is no harm in it at all but it maybe shows that people are losing sight of the context of music they listen to or play. The lack of contextual knowledge often shows up when I accompany student violinists at music festivals. They will typically announce their piece like this: 'I'm going to play Concerto in A Minor by Vivaldi' - when actually they are only playing a single movement from a three-movement work.
For those going on to study music as a profession at universities or conservatories, it must be a steep learning curve to get the background knowledge needed to write dissertations, programme notes etc., when it does not seem to be provided in many schools (certainly in UK).