Woe is one of my most used word to describe 'sad' (Next to doleful and melancholy). The reason behind this is because it expresses sadness, and anguish. However it is contained in a solitary three-letter package.
woe [woh]
noun
1.grievous distress, affliction, or trouble: His woe was almost beyond description.
2.an affliction: She suffered a fall, among her other woes.
interjection
3.
an exclamation of grief, distress, or lamentation.
Origin:
before 900; Middle English wo (interjection and noun), Old English wā (interjection) (cf. wellaway); cognate with Dutch wee, German Weh, Old Norse vei, Latin vae
Synonyms
1. anguis