What defines a compound word?

A compound word is defined as a word formed by combining two or more smaller words, or parts, to create a new word with a specific meaning. This process involves the merging of these distinct elements, which can be nouns, verbs, adjectives, or adverbs. For example, 'notebook' is a compound word made from 'note' and 'book.' When the two are combined, they create a new word that conveys a different idea than either part alone.

The other options do not accurately represent compound words. Words formed from synonyms refer to different words with similar meanings, which is not pertinent to the structure of a compound word. Contractions are formed by combining two words and often omitting some letters (like 'can't' from 'cannot'), but this does not entail the same process as creating a compound word. Lastly, words derived from a single root pertain to morphological processes where suffixes or prefixes are added to a singular root word, rather than the combination of separate words into a compound. Therefore, the defining characteristic of a compound word is the presence of two parts that, when combined, produce a unique meaning.