How do you address a baronet or knight?

Sir Walter Elliot, Bt, walking with 
Colonel Wallis by H Thomson (1897)
From Persuasion by Jane Austen (1897 edition)
Jane Austen rarely wrote about peers of the realm, but her books do contain a fair smattering of baronets and knights—the subject of this post.

In this post I answer the following questions:

Are baronets and knights peers?

Are the titles hereditary?

How do you address a baronet or a knight?

How do you address a baronet’s wife or a knight’s wife?

How do you address a baronet’s wid...