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In the previous topics, we have learnt how to add, subtract, multiply and divide to combine variables and constants to frame the algebraic expressions.

Let us recall a few basic concepts about expressions.

**1**. What is a binomial expression?

An expression which contains only \(2\) terms separated by operation addition or subtraction are called as binomial expression.

Consider the expression \(6y + 2\). In this, the expression is obtained by multiplying the variable \(y\) with the constant \(6\) and then adding the number \(2\) to the product.

Here, \(6y\) is the variable term, \(y\) is the variable, \(6\) is the coefficient of \(y\) and \(2\) is the constant term.

**2**. What are like terms?

Terms which have the same variables are called as like terms.

The terms \(6y\), \(3y\), \(10y\) are examples of like terms.

**3**. What are unlike terms?

Terms having different variables are called as unlike terms.

The terms \(-5x\), \(-3y\) are examples of unlike terms.

When we add or subtract like terms, we get a new term. But, when we add or subtract unlike terms, we get a new expression.

Consider adding the like terms \(3x\) and \(4x\), we get, \(3x + 4x = 7x\).

Now, consider adding an unlike term \(6x\) and \(2y\), we get, \(6x + 2y\).