Fazed and phased are commonly confused words (like unfazed and unphased).
Fazed is the past participle or simple past form of the regular verb “faze,” which means “to disturb or upset” (e.g., “The interview questions were difficult but did not faze her at all”).
Phased is the past participle or simple past form of the regular verb “phase,” which means “to carry out in phases” (e.g., “The transition to the new system will be phased over six months”).
However, we normally use the phrasal verbs “phase in” and “phase out” to express the gradual introduction of a change (e.g., “The new system will be phased in slowly/The old system will be phased out slowly”).
The QuillBot Grammar Checker can help ensure you’re using words like “fazed” and “phased” correctly.