TA: Support and Resistance

支持和阻力，很重要的两个股市术语。

定义 (Definition)

Support: the price level that a stock or market seldom falls.
Resistance: the price level that a stock or market seldom surpasses.

In almost every case, a stock will have both a level of support and a level of resistance and will trade in this range as it bounces between these levels. This is most often seen when a stock is trading in a generally sideways manner as the price moves through successive peaks and troughs, testing resistance and support.

Why Does it Happen?

支持和阻力线对于市场心理和供需是两大重要因素。

Support and resistance levels are the levels at which a lot of traders are willing to buy the stock (in the case of a support) or sell it (in the case of resistance).

When these trendlines are broken, the supply and demand and the psychology behind the stock's movements is thought to have shifted, in which case new levels of support and resistance will likely be established.

整数与支持阻力线间的关系

Round numbers like 10, 20, 35, 50, 100 and 1,000 tend be important in support and resistance levels because they often represent the major psychological turning points at which many traders will make buy or sell decisions. It is the increased buying and selling pressure at these levels that makes them important points of support and resistance and, in many cases, major psychological points as well.

Role Reversal (角色转换)

当价格冲破了支持或者阻力线，该线的角色会开始转换。比如说当价格冲破了一个阻力线，那该阻力就会变成下一个趋势的支持线，反之亦然。因为当价格冲破支持或者阻力线时，供需就已经改变，所以才会发生这样的现象。不过，要产生这样的现象，一定要是由强劲的一股冲力造成的。

支持与阻力线的重要性

分析支持与阻力线能帮助投资决策，和观察走势的转变。

For example, if a trader identifies an important level of resistance that has been tested several times but never broken, he or she may decide to take profits as the security moves toward this point because it is unlikely that it will move past this level.

As long as the price of the share remains between these levels of support and resistance, the trend is likely to continue. It is important to note, however, that a break beyond a level of support or resistance does not always have to be a reversal. For example, if prices moved above the resistance levels of an upward trending channel, the trend has accelerated, not reversed. This means that the price appreciation is expected to be faster than it was in the channel.

Traders should avoid placing orders at these major points, as the area around them is usually marked by a lot of volatility.

Do not place orders directly at the support or resistance level. This is because in many cases, the price never actually reaches the whole number, but flirts with it instead. So if you're bullish on a stock that is moving toward an important support level, do not place the trade at the support level. Instead, place it above the support level, but within a few points. On the other hand, if you are placing stops or short selling, set up your trade price at or below the level of support.




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ps: Content and pictures in this article are excerpted from Investopedia.