Specific Risk

What it is:

Specific risk is a discrete risk to which only a specific asset or type of asset is exposed. It is the opposite of systematic risk.

How it works/Example:

Specific risk is the risk of an event occuring that would directly or indirectly affect the market value of an asset or particular group of assets. For example, a rumor of a shortage of raw silicon is a specific risk to which computer and high-tech stocks would be exposed. Specific risk should not be confused with systematic risk, which is the risk of an event that would directly affect the entire market (e.g. recession, etc.)

Why it Matters:

Since specific risk affects only a type of asset in a market and not all assets, specific risk can be mitigated by diversification. In fact, all expected rates of return are calculated without specific risk because the assumption is that any rational investor is capable of diversifying away specific risk. If you fail to diversify (which means you're taking on more risk) you cannot expect to receive higher reward. 

Best execution refers to the imperative that a broker, market maker, or other agent acting on behalf of an investor is obligated to execute the investor's order in a way that is most advantageous to the investor rather than the agent.