Neologisms

Compounding

Two separate words are put together and acquire a new meaning. Compound words are first used together, then get hitched with a hyphen and then frequently become a single unit: face-lift, homesick.

Portmanteaus (blending)

A new word is created by joining not two complete words, but parts of words—with or without an overlapping part: moviewoke, flexitarian.

Acronyms

Words formed from the initial letters of a phrase. Some terms are pronounced as single letters (FYI, B2C), some are pronounced as a succession of letters and sound like a word (bogof): FYI, B2C, bogof.

Loan words

Words that are borrowed from other languages: tattoo (Haitian), tsunami (Japanese).

Clipping

A major part of the word, either the back or the front, is left out, the rest serves as a substitution for the whole word: gym(nasium), (tele)phone.

Conversion (functional shift)

Words undergo a change of word class (a noun becomes a verb, a verb becomes a noun, etc.): a friend -> to friend someone, a commuter -> to commute.

Repurposing (semantic shift)

A word is taken from one context and applied to another, often in a metaphorical sense: mouse, bug, net, web.

Eponyms

A person, place, or thing after whom or which something is named. For a while, they continue to be spelled with capital letters

Derivation

A prefix (in-, pre-, anti-, inter-, etc.) or a suffix (-ness, -ism, -ship, -ish) is added to a word and thus creates a new word with a new meaning that is likely to belong to a different word class: co-parent, defogabilisation.