What does morphology study in relation to words?

Morphology focuses on the patterns of word formation and the meaningful units within those words. This area of study delves into the smallest units of meaning, known as morphemes, which can be roots, prefixes, or suffixes. Understanding morphology allows individuals to analyze how these components combine to form new words, change meaning, or alter grammatical functions. For instance, recognizing that "unhappiness" consists of the prefix "un-", the root "happy", and the suffix "-ness" illustrates how morphology contributes to word formation and meaning.

The other areas mentioned in the other choices, such as sentence structure, contextual meaning of words, and grammatical rules, are encompassed in different linguistic disciplines, such as syntax and semantics, which focus on larger units of language and how meanings can change depending on context or grammatical rules. Morphology, however, is specifically concerned with the internal structure of words themselves.