943: -er (Agentive) Jul 9, 2017

In English, for the most part, different parts of speech are fairly distinct. It is possible to have one word that belongs to multiple lexical classes, e.g. 'water' in "one waters plants with water" is a verb and noun respectively, but alternatively various derivational suffixes can work to modify a word in a way that changes the part of speech to which it belongs. The suffix '-er', among its many other uses, can be added to most transitive verbs, i.e. ones that take direct objects, to become a noun indicating that someone performs said action. In this way, "she walks (dogs)" can become "the walker (of dogs)". There are a few exceptions however, such as "he knows many facts" would likely not become "the knower (of many facts)". It is not impossible to have that sentence, and it would probably be understandable to most people, but this would sound odd.