Sour

Lemons have a sour taste.

All sour things, as vinegar, provoke appetite.

A few types of molecules get sensed by receptors on the tongue. Protons coming off of acids ping receptors for "sour." Sugars get received as "sweet." Bitter, salty, and the proteinaceous flavor umami all set off their own neural cascades.

Don't drink that milk; it's turned sour.

His sour breath makes it unpleasing to talk to him.

He gave me a sour look.

He was a scholar […] / Lofty and sour to them that loved him not, / But to those men that sought him sweet as summer.

a sour marsh

sour gas smells like rotten eggs

Let me embrace thee, sour adversity

The result may not quite give the Wearsiders a sweet ending to what has been a sour week, following allegations of sexual assault and drug possession against defender Titus Bramble, but it does at least demonstrate that their spirit remains strong in the face of adversity.

Unlike what the name implies, there is nothing inherently wrong with a sour note: It is perfectly well-tuned note that would sound normal in another context (and which presumably would not sound sour to someone unfamiliar with tonal music).

“You know I like them candies, especially the lemon sours.”

For many Years of Sorrow can dispense; A Dram of Sweet is worth a Pound of Sour

Too much lemon juice will sour the recipe.

So the sun's heat, with different powers, / Ripens the grape, the liquor sours.

To sour your happiness I must report, / The queen is dead.

He was prudent and industrious, and so good a husbandman, that he might have led a very easy and comfortable life, had not an arrant vixen of a wife soured his domestic quiet.

We broke up after our relationship soured.

stagnant water , which tends to sour the soil