melancholic(filled with or affected by melancholy) adjective [UK: ˌme.ləŋˈk.ɒ.lɪk] [US: ˌme.lənˈk.ɑː.lɪk]Sometimes he's happy, sometimes melancholic. = Unas veces está contento, otras melancólico.
mournful(filled with grief or sadness) adjective [UK: ˈmɔːn.fəl] [US: ˈmɔːrn.fəl]
pensive(looking thoughtful or sad) adjective [UK: ˈpen.sɪv] [US: ˈpen.sɪv]
plaintive(Sorrowful, mournful or melancholic) adjective [UK: ˈpleɪn.tɪv] [US: ˈpleɪn.tɪv]
wistful(sad and thoughtful) adjective [UK: ˈwɪst.fəl] [US: ˈwɪst.fəl]He has a wistful look on his face. = Él tiene una mirada melancólica en su rostro.