Final answer:
Words that end in 'sis' form plurals by changing 'sis' to 'ses', as in 'analysis' to 'analyses'.
Step-by-step explanation:
Words that end in sis form plurals by changing sis to ses. This is a standard rule for forming plurals for words that end in -sis in the English language.
For example, the word 'analysis' becomes 'analyses' in plural, and 'thesis' becomes 'theses'. This applies to all nouns ending in -sis, regardless of their position within a sentence or context. It's important to remember that these plural forms do not involve adding apostrophes or hyphenation.
Apostrophes are used to show possession, as in 'the children's game' or 'the workers' benefits'. On the other hand, the switch from -sis to -ses simplifies the pronunciation and follows the proper spelling rule for pluralization.