疼 (téng) and 痛 (tòng) both are words that can mean “ache and pain”. However there are many subtleties to how you can use them.
疼 has two different meanings. Its first meaning is ache/pain/to be sore. For example, 今天我头疼得很厉害 (My headache hurts like hell). Confusingly, it could also mean to love dearly, to be fond of, or to dote on. For example 孩子病了，妈妈很心疼孩子 (The child is sick and the mother feels distressed about her sweet heart).
痛 has three different meanings. Similarly to 疼, 痛 can also mean ache/pain like in 今天我没去上课，因为我肚子痛 (Today I didn’t go to class, because I got tummy ache.). 痛 could also mean sadness, sorrow, or grief. For example 痛’s use in the word 痛苦 (tòng kǔ) means painful. 痛’s third meaning is extremely, deeply, or bitterly likeit’s use in “痛哭” (tòng kū), which means to cry bitterly.
In short, 疼 can also mean ‘to love deeply’, and you can add an object, whereas 痛 doesn’t contain this meaning,and cannot add an object.
Both 疼 and 痛 can mean ache and pain, but what is the difference between them when they both express ache and pain? Here are a few things to help you understand difference and recognize the intended meaning.
Physical vs Emotional Pain
疼 focuses more on physical pain, whereas 痛 can be used to mean both physical pain and emotional pain. For example: His friend cheated him, he feels pain in his heart (他的朋友骗了他，他觉得很心痛).
Speed of Pain
疼 expresses acute and sharp pain which happens suddenly. Suppose your hand is stuck by a door. In English you might say “Ouch!” In Chinese, people would probably say 疼死了 rather than 痛死了. On the contrary, 痛 indicates chronic, deep and long lasting pain. Therefore, 疼 can express the instant feeling of pain.