(听勁 simplified, 聽勁 traditional)
The character ting is comprised of an ear, an eye and the heart/mind and also a pregnant woman. Jing/Jin is a plough and a cultivated field.
Jing also transliterated as jìn (勁) translate as strength or power in the martial sense, Li (力) also translates as strength. jing/jìn is a trained, cultivated strength as opposed to brute force. Ting jìn is the martial art notion of listening, with the body not the ears, for an opponent’s jìn. The projection of jìn is fā jìn (發勁) fā is to show, to issue and develop. Tai Chi Literature also talks of learning dong jìn (懂勁) which is the ability to understand or comprehend jìn.
Many western authors translate jìn as energy. Not to be confused with the more familiar notion of qi (氣) this is the energy, or vital breath flowing through our body. Qi (氣) figuratively means the energy we extract from the air and food as it is derived from combining the characters for rice and air.
Another jing (精) said slightly differently, is our essence as in bodily fluid. This is both derived from food and inherited from our parents at conception. This jing (精) was regarded as finite resource by some Daoist sects, and is expended and lost (by men, not women) during intercourse, hence the notion of celibacy promoting longevity, an important goal for these early Daoists.
Qigong practices, energy cultivation exercises, including tai chi seeks to transmute Jing/essence (精) into qi/energy(氣), then into shen/spirit (神), this is first done by concentrating and storing qi into the abdomen, the dantian (丹田) an important energy field.Further Reading: Tai Chi Chuan: Decoding the Classics for the Modern Martial Artist.