Is Dotard a Noun?

A dotard is a person who's old and senile. The noun dotard used to be a standard way to insult someone by implying that they were physically and mentally decrepit. Shakespeare, Chaucer, and J.R.R. Tolkien all used it regularly as a put-down between characters.

Is Senile a noun or verb?

the state of being senile, especially the weakness or mental infirmity of old age.

Is manual a noun or adjective?

The word manual comes from Latin root words meaning "of the hand," and the adjective form of the word still maintains that meaning — "by hand or of the hands." The adjective definition is also extended a bit to mean something done by hand and not machine, and the implication is usually that it is physical work.