sensitivity

Sensitivity is how easily something reacts or is hurt. Great sensitivity, sensitivity to light, handled with sensitivity.

Of a person it means both being easily upset and being good at noticing other people's feelings — two quite different things sharing one word. In medicine, sensitivity to something means reacting badly to it, and in testing, sensitivity is how well a test detects what is really there, against specificity. In equipment it is how small a signal a device can pick up. Note sensitive, and oversensitive.