【Sour】 , 【acid】 ,  【acidulous】 ,  【tart】 ,  【dry】  mean having a taste devoid of sweetness.

All but  【dry】 suggest the taste of lemons, vinegar, or of most unripe fruits.

【Sour】  and  【acid】  are often interchangeable, but  【sour】 is more likely to be chosen to describe something that through fermentation has lost its natural sweet or neutral taste or, sometimes, smell and the term may additionally suggest a spoiled or rancid state.

【Acid】 , on the other hand, is appropriately used to describe something having a sharp sweetless taste in its natural state usually due to the presence of chemical acids.

【Acidulous】  and  【tart】  are applied, as a rule, to things which may be described as  【acid】 ,  【acidulous】  implying a modest degree of acidity and  【tart】 , a sharp but often agreeable acidulousness or, sometimes, acidity.

【Dry】  is usually applied to wines which, although without any sweetness, are bland and therefore neither definitely 【acid】 nor definitely 【sour】 . In their extended senses  【sour】 applies especially to what is crabbed or morose and  【acidulous】  and  【tart】 to what is characterized by asperity, pungency, or sharpness.

【Acid】 , partly by allusion to the corrosive powers of some acids, is likely to describe what is biting or caustic while  【dry】 may suggest matter-of-fact impersonal presentation of what is humorous, ironic, or sarcastic.