Why Nvidia’s longer-term future return is not worth the risk — even if it continues to be a phenomenally profitable company. Nvidia Corp.’s market performance over the past six months is a good illustration of the difference between a good company and a good stock.

Shares of Nvidia ( NVDA -4.86%) are falling on Monday. The company's stock lost 4.5% as of noon ET, but was down as much as 5.3% earlier in the day. The drop comes as the S&P 500 ( ^GSPC -0.05%) slipped 0.3% and the Nasdaq Composite ( ^IXIC -0.31%) lost 0.4%.