Semantic theming - fonts in typography

The main purpose of typography is to make the consumption of various kind of content ergonomic: first distinctive and recognizable, then easy to read and comprehend.

The kind of content defines the semantic categories for font characteristics set usually reflected in the purpose of content: 

• reading - text, headers, tips,... - Roboto, SourceSansPro
• script/code presentation - monospaced
• initialism  - lone symbol/ mini tags / acronyms - barley
• iconized - letter in/as icon, badge
• tag - icon label, tag without background/border

Each category most likely will use own set of typeface, font type and font properties like spacing, size, weight, etc. 

Lets go over each semantic typography category and explore the purpose and applicable properties.

READING - I guess it is self-explanatory. The sentences, paragraphs and pages of text should be easy to read for hours. Besides of font it defines ergonomics for eye and even neck: you do not want your reader to swing eyes and head righ-left while reading the multi line text. The newspaper columns are good samples or solving such problem. I still love the books with 2-column page layout.