Final answer:
To pluralize a medical term ending in 'us', the 'us' is usually replaced with 'i'. For instance, 'alveolus' becomes 'alveoli', following the traditional Latin rules for pluralization. Some terms may have exceptions due to language evolution and usage.
Step-by-step explanation:
To pluralize a medical term that ends in us, you typically remove the -us and add -i to the end of the root word. This morphological change follows the traditional rules derived from Latin, where many medical terms are sourced. For example, the plural form of alveolus is alveoli, and the plural form of focus is foci.
However, some medical terms could deviate from this pattern due to common usage evolution over time, thus, it's essential to be aware of exceptions. In the medical field, accurate communication is vital, so it's important to learn and use the correct plural forms of these terms.