✅ Acrid describes something that tastes or smells biting or sharp or that irritates the eyes and nose (Acrid smoke billowed across the sky).

✅ Astringent describes something biting or caustic (The fruit is astringent and not too pleasant to eat).

✅ Although both acrid and astringent describe intense and often irritating tastes and smells, acrid tends to refer to things like smoke and gas, whereas astringent can refer to food or cleaning ingredients, such as vinegar or lemon juice.

✅ Sting means to cause a sharp, irritating pain (The burn started to sting when the water hit it).

✅ Smart means to cause, or feel, a sharp, especially irritating and stinging, pain (His hand smarted where he had accidentally cut it).

✅ Although sting and smart refer to similar types of pain, sting more often refers to a pain caused by something hurting you, whereas smart more often refers to the pain you feel during or after being hurt (The cold rain stung her skin; Her twisted ankle still smarted after a few weeks).

✅ Balk means to stop and refuse to go on (The horse balked at the sight of a lizard).

✅ Demur means to object to or show reluctance toward something, especially based on scruples (I demurred when I was offered an extra bag of apples under the table).

✅ Although both balk and demur mean to object to something, balk suggests a sudden and stubborn refusal to continue or to go on, whereas demur has a less stubborn connotation (At first I demurred, but I accepted after hearing their perspective; He balked at the dangerous river crossing and decided to go home).