$6x^6+15x^4-3x^2$  

 $5x^4+15x^2-3x^{3\ }$  

 $6n^4-2n$  

 $6n^5-4n^4$  

 $16y^7-10y^4$  

 $16y^7-10y^5$  

 $6m^8-18m^6-6m^4$  

 $54m^8-18m^2-6m^5$  

 $54m^{8\ }-18m^6-6m^5$  

Is an expression containing two or more algebraic terms

is an expression containing one algebraic terms