Wolfram Language & System 10.4 (2016)|Legacy Documentation
|Coefficient[expr,form]||coefficient of form in expr|
|Exponent[expr,form]||maximum power of form in expr|
|Part[expr,n] or expr[[n]]||n term of expr|
You may notice that the function Part[expr,n] used to pick out the n term in a sum is the same as the function described in "Manipulating Elements of Lists" for picking out elements in lists. This is no coincidence. In fact, as discussed in "Manipulating Expressions like Lists", every Wolfram Language expression can be manipulated structurally much like a list. However, as discussed in "Manipulating Expressions like Lists", you must be careful, because the Wolfram Language often shows algebraic expressions in a form that is different from the way it treats them internally.