In financial terminology, the expressions 'Bullish' and 'Bearish' are primarily used to describe trends in which of the following sectors?

The correct option is Stock Market.

Understanding Bullish and Bearish Trends:

In financial terminology, the terms 'Bullish' and 'Bearish' are fundamentally used to describe market sentiment and price movements in financial markets, particularly the Stock Market.

1. Bullish Trend:
A bullish market refers to a period where stock prices are rising or expected to rise. Investors who believe that prices will go up are called "bulls." The term comes from the way a bull attacks by thrusting its horns upward into the air.

2. Bearish Trend:
A bearish market refers to a period where stock prices are falling or expected to decline, usually marked by a drop of 20% or more from recent highs. Investors who expect prices to fall are called "bears." The term comes from the way a bear attacks by swiping its paws downwards.

Therefore, these expressions are primarily used to indicate upward or downward trends in the Stock Market.