A circle is a collection of all points which are at a constant distance from a fixed point. The fixed point is called the **centre** of the circle. A line segment joining centre of the circle to a point on the circle is called **radius** of the circle.

Quadrilateral is a plane, closed, geometric figure with four sides. A quadrilateral has four sides - AB, BC, CD and DA, four angles - ∠A, ∠B, ∠C, ∠D, two diagonals - AC and BD, and four vertices - A, B, C and D.

The angles opposite to equal sides of a triangle are equal. The sides opposite to equal angles of a triangle are equal.

Two lines can either be parallel or intersecting. Three lines may be parallel to each other, intersect each other in exactly one point, intersect each other in two points (transversal), or intersect each other at most in three points.

Triangles is a a plane figure bounded by three line segments. The sum of the three interior angles of a triangle is 180º.

Line Segment is the portion of the line between two points A and B. A line segment has two end points. Ray is a line segment AB when extended in one direction.

Percent means per every hundred and denoted by the symbol %. A fraction with denominator 100 is called a Percent.

Sequence or progression is a group of numbers forming a pattern. Arithmetic Progression (AP) is a progression in which each term, except the first, is obtained by adding a constant to the previous term.

Quadratic polynomial is a polynomial of degree 2. Quadratic equation is an equation having degree 2. General form of a quadratic equation is **ax ^{2} + bx + c = 0**, a ≠ 0 where a, b, c are real numbers and x is a variable.

Linear polynomial is a polynomial having degree 1. Equation means two expressions separated by sign of equality. Thus, linear equation involves only linear polynomials - An equation in which the highest power of the variable is 1.

Algebraic expressions are a combination of constants and variables, connected by any or all of the four fundamental operations (+, -, ×, ÷).

**Natural Numbers (N)** are Counting numbers - 1, 2, 3, 4, and so on. The smallest natural number is 1. **Whole Numbers (W)** are Natural numbers including 0 - 0, 1, 2, 3, 4 , and son on. The smallest whole number is 0.

India is said to be the land of farmers and these farmers are mostly living in the rural India. Various types of agricultural activities are found in different parts of the country. Agriculture is categorised into different types on the basis of purpose of farming.

The diversity of plants and animal provide us food, fuel, medicine, shelter and other essentials without which we cannot live. Bio-diversity is a short form of biological diversity. In simple terms, bio-diversity is the total number of genes, species and ecosystems of a region. It includes (i) genetic diversity (ii) species diversity and (iii) eco-system diversity.

India has **monsoon** type of climate. The word ‘monsoon ‘refers to the seasonal reversal of the wind direction in a year. Due to this, India has four prominent **seasons** - cold weather season, hot weather season, advancing southwest monsoon season and post or retreating monsoon season.

India is the seventh largest country of the world. It extends from the state of Jammu and Kashmir in the North to the state of Tamil Nadu in the South; from the state of Arunachal Pradesh in the east to the state of Gujarat in the west.

The Constitution of India has made alternate provision for the structure and functioning of all the three branches of the government - executive, legislature and judiciary, The President, the Council of Ministers with Prime Minister constitute the executive branch of the Government, the Parliament with its two houses - House of the People or Lok Sabha and Council of States or Rajya Sabha is the legislative branch and the Supreme Court heads the judicial branch.

India is a Federation having governments at two levels - State level and Union or Central level. The three branches of government - executive, legislature and judiciary exist and function at both the levels.

Local Government is a government of the local people. Being located nearest to the local people, local government institutions are under constant observation of the society. The Government of India has empowered the institutions by 73rd and 74th Constitutional Amendment Acts 1992, so that they may work for the welfare of the local people in a more effective manner.

In a Democratic Country like India certain basic and fundamental rights have been granted to every citizen, but in many parts of the world people are still struggling for these rights.