Let's start with crows. A crow refers to a kind of bird. They like to sing with their mouths, and their calls are quite distinctive. They will make a "whoa, whoa, whoa" sound. Crows grow up to be huge, reaching about 50 cm. They belong to social birds and are fierce omnivorous birds. Besides eating millet, wild fruits and insects, we often eat other birds, including adults.
However, crows have always had a bad reputation. Besides personality, it is also related to its voice and feathers. In my hometown, if you hear a crow, or meet a crow landing on the roof, great things may happen to this family. There is a good chance that someone will die. However, this is all groundless. The reason why this matter is mentioned is only to prove that people regard crows as "unlucky birds", but whenever they meet them, they will hide or feel unlucky.
In addition, the word "black" in "All Crows are Black" refers to the color of crows. Because crows are all over the world, most crows have black feathers, so this sentence conforms to the laws and phenomena of nature. When people mention crows, they naturally think of "black" in their minds. But this sentence is often used to describe a certain social phenomenon, such as all officials are corrupt, all businessmen are smart, all cats eat fish and all dogs are popular. Although the word says "crow is as black as a crow", it implies some common views that are not recognized by the world.
The so-called "black", its meaning and explanation will change with the application scene of "the crow in the world is generally black". For example, describing an official refers to the defects (bad habits) existing in most officials, such as corruption, lewdness and being good at flattery.
If this sentence is applied to other aspects, such as teachers in the education industry, it may be that teachers accept red envelopes and force students to buy handheld computers. In short, "black" is not really black, it refers to the color of crow feathers, and it also alludes to some social phenomenon, which means that a group of people have the same habits or problems.