General properties: Arabic numerals: 2 Pronunciation: èr dialect: n √ lowercase: two big letters: two special symbols: 2 √ 2 √ 2 English: two (even: two) seconds (ordinal number, second), twice counting symbols: Roman numerals: II binary: 10 hexadecimal:. It's called even number. For even-numbered integers, such as 10, 16, we only need to judge whether the last digit is even, while binary only needs to judge whether the last digit is 0.2, which is the smallest, the first prime number (also called prime number) and the only even prime number. The next prime number is 3. Because there is more than one. The next height composite number is 4.2, and the third Fibonacci number is the 1 th positive prime number in Fibonacci sequence. 2 is a unique Planck number. 2 is the smallest number that can be decomposed into the sum of two nonzero complete squares: 2 = 1+ 1. The simplest nontrivial group has an order of 2, that is, the remaining groups have an order of 2. Quadratic function: y = ax 2+. C is a constant) Quadratic curve called x: also known as conic curve, it is the most thoroughly studied curve except straight line in history. Quadratic equation: the lowest nonlinear equation with general solution formula. The simplest finite generating noncommutative group. Dichotomy: If two propositions contradict each other, then one of them must be wrong. Quadratic reciprocity law: classic. Was discovered by gauss. For any number p:p+p=2p, addition becomes multiplication. P× p = p 2, multiply to power. Pp = p↑↑2, power-variable quartering. The smallest object has two elements. The arithmetic square root of 2 is the earliest irrational number discovered. Edit the atomic number of helium in this section of Science. Two-force synthesis: if one force produces the same effect as two forces. This force is called the resultant force of the two forces, and finding the resultant force of the two forces is called the condition of the balance of the two forces: if the two forces acting on an object are equal in magnitude and opposite in direction, they will balance each other on the same straight line. Newton's second law of motion: law content: the acceleration of an object is directly proportional to the resultant force F acting on it, and inversely proportional to the mass of the object. The direction of acceleration is the same as that of external force. In other fields: Europe, South Africa, the Middle East and Japan are the representatives of the DVD field. Year: 2 years, 2 years BC, 1902. Idiom: You can't use two things at the same time. Philosophy: Dualism, Dichotomy. Biology: diploid, that is, an organism with two chromosomes in its somatic cells. Like people. In nature, the number 2 is the most active. It always appears in the natural science we study and in our life. Chemical formula: Many elemental gases on the earth are X2. In other words, they are composed of two x atoms. O2，N2，H2，Cl2，F2。 Lots and lots. Many things on us also appear in pairs. From top to bottom, you can also find many. If there is no opposition between the left and the right, I'm afraid people can't even stand. It is also symmetrical. A piece of paper folded in half presents us with two identical worlds. Whether insects or mammals, the number of legs must be a multiple of 2, otherwise how can they survive? The mirror also shows us two consistent worlds. Some grammars in English reflect some special meanings of 2. For example, I already have two apples, and I want the third apple, so I want to use the second one. So 2 also represents another meaning: extra, other. 2 is a fence from singular to plural. Other meaning: Sometimes it is used to describe a simple-minded person. Stupid behavior. Xiaobei, for example, is really stupid. Of course, sometimes it can also show that a person is unique, stylish and cute. There is a saying called "very bright". There are two meanings, one is positive and the other is negative. The positive meaning means that this person is simple and lovely, and the negative meaning means that this person is an idiot. Another one is stupid and derogatory. This function is also equal to two. For example, Nice 2 meets u, which also represents a binary number. Example:100011kloc-0/In the crowd: 2 means double knives, which is called bisexuality.