* Class: This is a base word that can be modified with prefixes and suffixes (e.g., classmate, classify).
* Mass: This is a base word that can be modified with prefixes and suffixes (e.g., massive, mass-produced).
* Pass: This is a base word that can be modified with prefixes and suffixes (e.g., passport, passing).
* Press: This is a base word that can be modified with prefixes and suffixes (e.g., pressure, pressing).
* Cross: This is a base word that can be modified with prefixes and suffixes (e.g., crossroads, cross-examine).
It's worth noting that many words ending in "ss" are actually plural forms of words ending in "s" (e.g., "glasses," "busses," "kisses").