Odd numbers can be negative numbers. In the set of integers, odd numbers refer to integers that are not divisible by 2. They can be positive, zero or negative. For example,-1, -3, -5, etc. They are all negative odd numbers, because they are not divisible by 2 and are negative numbers. Similarly, 1, 3, 5, etc. They are also positive odd numbers, because they are not divisible by 2 and are positive numbers.

Odd numbers and even numbers are two important subsets of integer sets, where odd numbers are integers divisible by 2 and even numbers are integers divisible by 2. Whether it is a positive number or a negative number, it is an odd number as long as it is not divisible by 2.

Negative number is a concept in mathematics, which is used to represent real numbers less than zero. A positive number means a real number greater than zero, and a negative number means a real number less than zero. Here are some introductions about negative numbers:

Definition: A negative number refers to a real number less than zero, and its sign is usually the minus sign "-". For example, -3, -2,-1 are all negative numbers.

Number axis: Number axis is a graphic tool used to represent real numbers on a straight line. On the number axis, positive numbers are on the right of zero and negative numbers are on the left of zero. A negative number is indicated by adding a negative sign before the corresponding number.

Comparison: Negative numbers can also be compared. The smaller the negative value, the closer it is to zero, and the larger the negative value, the farther it is from zero. For example, -5 is less than -3, because -5 is closer to zero.

Operation: Negative numbers can participate in various mathematical operations, such as addition, subtraction, multiplication and division. For example, -2+(-3) = -5 means adding -2 and -3 to get -5.

Absolute value: the absolute value of a negative number is the value after the sign is removed. For example |-5| = 5, that is, the absolute value of -5 is 5.

Properties of negative numbers: negative numbers have some special properties, such as multiplying two negative numbers to get a positive number (for example, -2 × -3 = 6), and multiplying a positive number with a negative number to get a negative number (for example, 2 × -3 = -6).

Negative numbers are widely used in mathematics and real life. They can be used to express concepts such as debt, loss and sub-zero temperature. The introduction of negative numbers expands the scope of mathematics, which enables us to better describe and deal with negative values and negative vectors.