Final answer:
Compounding is the word formation process where two or more words are combined to form a new word, which can be written as one or separately, such as 'blackbird' or 'cattail'.
Step-by-step explanation:
The type of word formation that combines two or more words to make a new word that can be written as one or separately is called compounding. In compound words, each part is known as a stem, and these words are formed through the simple addition of at least two free stems. For instance, when combining 'black' and 'bird', we get the compound word 'blackbird'. This process can also result in double letters; for example, combining 'cat' with 'tail' produces 'cattail', where 't' from both stems comes together.
Examples of unusual spelling in compound words include 'cupboard' ('cup' + 'board') and 'raspberry' ('rasp' + 'berry'), where the spelling doesn't directly reflect the pronunciation. Furthermore, in words where palatalization occurs, such as when combining 'dis' with 'gestion', we produce a word with [ch] spelled as , resulting in 'digestion'.