Faze is a verb meaning to disturb, disconcert, daunt, worry or put off one’s stride.

• The noisy heckling from the crowd did not faze the candidate.
• She was not fazed when a piece of scenery fell over, but continued dancing.

Phase is a noun meaning a period or stage such as a phase of the moon, the latest fashion phase or a phase of somebody’s career.

• He’s just going through a difficult phase in his life.
• There was a phase of wearing mini-skirts in the 60s even in the depths of winter.

Phase is also a verb meaning to plan or carry out systematically, usually followed by in or out. For example, when you implement a plan little by little, you phase it in. When you abandon a plan little by little, you phase it out.

• The memo described how the unsuccessful night courts were to be phased out as quickly as possible.
• The new benefit changes would be phased in over the next two years.

Here’s a composite example to finish:

• Don’t be fazed if your toddler is going through a phase.