What is morphology?

Source

Morphology is the study of how words are formed and how they interact with each other.

The word unkindness, for example, consists of a root or stem (kind). a prefix (un) and a suffix (ness). A change in one of these morphemes or their addition/subtraction creates a new word. An example would be to add another suffix es to create a plural: unkindnesses

Inflection 

English is what linguists call a 'weakly inflected' language.  This means that there are fewer rules to remember. 

For personal pronouns, for example, English has three cases: subjective (I, you, he etc), objective (me, you, him, her, it, us, them) and possessive (my, mine; your, yours etc).

Other languages have many more variants. 

Is English the easiest language to learn?