Jing

Jing (勁; spelt Jīng or Jīn also known as Nei Jin or Fa Jin--meaning 'power' or 'energy') are options for directing ones energy, (both internal and external,) and were first mentioned by Bumi in the episode Return to Omashu. Jing that have been mentioned correspond to tactics and strategies in battle. A parallel to the series' concept of "jing" would be the 'Fight or Flight' response in psychology - certain personality types are more dispositioned for a particular type of jing.

Types
According to Bumi, there are (at least technically) 85 distinct types of jing, although only the main three have been named so far:
 * Positive jing, corresponding to advancing or attacking.
 * Negative jing, corresponding to retreating or evading.
 * Neutral jing, corresponding to waiting and listening (or, as Bumi described it as, "doing nothing".)

Positive Jing
Positive Jing is mostly exercised in Firebending and complements the aggressive tactics of Firebenders during combat. Firebenders will prefer pre-emptive strikes, to attack first and to come at their opponents with full force and overwhelming them with sheer power. These 'Positive Jing' attributes are also found in the attitudes and the willful natures that are common amongst the people of the Fire Nation.

Negative Jing
Negative Jing is mostly exercised in Airbending, echoing the Air Nomad's non-aggressive lifestyle and their philosophy that all life is sacred, and only fight as a last resort if conflict cannot be avoided. Airbender's are more mobile fighters compared to Earthbenders, and possess a highly dynamic fighting style. A comment made by Bumi in The King of Omashu highlights that in combat, to "avoid and evade" is a "typical Airbender tactic".

In the case of Waterbending, following the moon and the oceans's example of 'push & pull', a Waterbender will alternate between and maintain a balance of both positive and negative jing in combat in order to allow for them to turn their defense into their offense as they turn their opponent's force against them while conserving their own energy. The Waterbender's fighting style of turning their opponent's force against them is based on how the moon reflects light rather than gives off its own.

Neutral Jing
Neutral Jing, however, is the key to Earthbending. Fundamentally, neutral jing will involve listening, (though seemingly doing nothing,) and waiting for the right moment for them to strike. When in combat, an Earthbender is more a stationary fighter compared to an Airbender, and will usually wait for their opponent to come to them, they will stand their ground and meet their opponent's attacks head-on, before delivering a strike of their own.

As highlighted in Season 2, someone who has mastered neutral jing is someone who waits and listens before striking. Bumi relies on neutral jing during his Earthbending, to the extent that he refuses to flee Omashu even when Aang comes to rescue him. His desire to wait for an opportune moment to strike was initially baffling to his soldiers and to Aang, although Aang later accepted Bumi's decision. Bumi eventually frees himself on the Day of Black Sun, which he realized was the right time to strike because it was the moment when all Firebenders lost their powers.

Quotes
Discussion about the concept of jing between Avatar Aang and King Bumi:


 * Aang: I don't understand. Why didn't you free yourself? Why did you surrender when Omashu was invaded? What's the matter with you, Bumi!?
 * King Bumi: Listen to me, Aang. There are options in fighting, called jing. It's a choice of how you direct your energy...
 * Aang: I know! There's positive jing when you're attacking, and negative jing when you're retreating...
 * King Bumi: ...and neutral jing when you do nothing!
 * Aang: There're three jings?
 * King Bumi: Well, technically, there are eighty five. But, let's just focus on the third. Neutral jing is the key to Earthbending. It involves listening and waiting for the right moment to strike.
 * Aang: (with dawning understanding) That's why you surrendered, isn't it?
 * King Bumi: Yes, and it's why I can't leave now.
 * Aang: I guess I need to find someone else to teach me Earthbending.
 * King Bumi: Your teacher will be someone who has mastered neutral jing. You need to find someone who waits and listens before striking.

(Momo jumps onto Aang shoulder and chitters)
 * Aang: Hey, Momo!
 * King Bumi: Momo's mastered a few jings himself!

Trivia
Дзинг
 * Knowledge of Jing seems to be well known or at least common knowledge at least 100 years ago, as many Earthbenders do not use Jing properly, but Aang and Bumi seem to know perfectly well what it is.