I am a bit confused with the usage of the terms root, lemma and stem. My understanding of the terms are as follows.
Root:The central (free) morpheme which has the content to which other bound morphemes are added so as to form a word.
Lemma: An inflected form that acts as a head. It represents all the inflected word forms of a given root, when used independently like in a dictionary.
Stem: The portion of strings that are common in all the inflections of a word.
I am further confused, when it comes to the derived words. For example, if I am dealing with the inflection 'drivers'. What is the lemma of the word, and what is the `root' of the word?