Not sure.
There is no particular name for x2 and 2xy (both include x) in x2 + 2xy + y2 + y3
Terms that contain the same variable is called "like terms".
If the variable exists in all the terms, include it.
There is no simple answer. For example 3x^2y and 4 xy^2 have the same variables, x and y. But there is no name for such two terms.
They are 'like' terms
like terms
Like terms
Similar terms or like terms are terms with the exact same variable and the variable have the exact same exponents. So x2 and 2x2 are like terms but x2 and x are not.
Terms that contain the same variable is called "like terms".
like terms
like terms
Like terms.
dissimilar terms are terms that do not have the same variable or the variable do not contain the same number of exponents