penthos: grief, public expression of grief by way of lamentation or keening
See also akhos.
As with akhos, penthos describes both the feeling of grief and its expession through song. A song of lamentation can incorporate both singing and crying, and the weeping, although it may include being choked up with tears flowing and nose running, is considered part of the form of the song. For a humorous example that shows a contrast between artificial vs. natural expressions of grief, see Saturday Night Live's skit on the Funeral of Superman.
Laments and love songs often express similar sentiments. The two types of song can sound very similar because love songs are most often about unrequited love. For a more modern example, compare Vivialdi's "Sposa, son disprezzata," as sung by Cecilia Bartoli. In ancient Greek song culture, women sang love songs/laments for the hero Achilles, who by his death as a beautiful young man inspired this sort of erotic grief.
For more on penthos in Homeric epic, see The Best of the Achaeans, chapter 6, paragraphs 2-4.