sad / sad/ • adj. (sad·der, sad·dest) 1. feeling or showing sorrow; unhappy: I was sad and subdued. ∎  causing or characterized by sorrow or regret; unfortunate and regrettable: he told her the sad story of his life.2. inf. pathetically inadequate or unfashionable: somebody's priorities are pretty sad.DERIVATIVES: sad·dish adj.sad·ness n.

sad
A. †sated, weary OE.; †steadfast, firm; †grave, serious; sorrowful XIV; deplorably disappointing or bad XVII.

B. †solid, dense XIII (cf. sad-iron, solid flat-iron); dark-coloured XVI; (of bread, etc.) that has not ‘risen’ XVII. OE. sæd = OS. sad (Du. zat), OHG. sat (G. satt), ON. saðr, Goth. saþs :- Gmc. *saöaz :- IE. *sətós, pp. formation (see -ED1) on a base repr. also by Gr. áatos (:-*nsətós) insatiate, L. sat, satis enough, satur sated, OIr. sathech satiated, Lith. sotùs satisfying.

Hence sadden (-EN5) (dial.) make solid XVI; make sorrowful XVII.

SAD (seasonal affective disorder) (sad) n. a disorder in which the mood of the affected person changes according to the season of the year. Typically, with the onset of winter, there is depression, general slowing of mind and body, excessive sleeping, and overeating. These symptoms resolve with the coming of spring and are also relieved by phototherapy. There is evidence that mood is related to light, which suppresses the release of the hormone melatonin from the pineal gland, but the exact mechanism by which light acts as an antidepressant is unclear.

SAD • abbr. seasonal affective disorder.

Sad systems analysis and design