What is the correct suffix for faith?

There isn't one single "correct" suffix for "faith." It depends on what you want to convey:

For nouns:

* -ful: This suffix means "full of," creating a noun like "faithfulness," meaning "the quality of being faithful."

* -er: This suffix means "one who," creating a noun like "believer," meaning "one who has faith."

* -ist: This suffix means "one who believes in," creating a noun like "theist," meaning "one who believes in God."

For adjectives:

* -ful: This suffix means "full of," creating an adjective like "faithful," meaning "having faith."

* -less: This suffix means "without," creating an adjective like "faithless," meaning "without faith."

For verbs:

* -en: This suffix can be added to some nouns to create a verb, like "strengthen" from "strength." This doesn't work directly with "faith," but you could use a related word like "strengthen" to convey strengthening one's faith.

Ultimately, the best suffix depends on the specific meaning you want to express.