This phaser will teach you vocabulary (and maybe stun you).

phase (noun): a particular appearance or state in a regularly recurring cycle of changes; a distinguishable part in a course, development, or cycle
phase (verb): to adjust so as to be in a synchronized condition; to conduct or carry out by planned phases
faze (verb): to disturb the composure of
—Merriam-Webster

Phase and faze sound the same. But this is where their similarities end. For instance, phase (both as a noun and a verb) deals with time; faze deals with emotion. Also, you can go through a phase in your life, and you can do the action of phasing in a new idea; however, someone else has to be the person who fazes you.

Let’s look at their etymologies to learn more about how they differ.

Etymology
Phase comes from the Greek word phasis, which means appearance (such as of a star). The stem is phainein, which means to show, to make appear. English began using phase in 1812 to describe lunar cycles (phases of the moon).[i]

Faze comes from the Old English word fesian, which means to drive away.[ii]

We can see that from the beginning phase dealt with cycles of time, and faze dealt with actions that disturb.

Using phase and faze
Now let’s look at some examples of phase and faze.

phase (noun): Five years ago, Kirk went through his awkward goth phase.
phase (verb): Kirk will phase in the new weapons technology.
faze (verb): Kirk is so self-assured that nothing can faze him.

Quiz
Do you think you have the differences down yet? Test your knowledge with this quiz. Fill phase or faze in the blanks. The answers are below.

1. In three months, the space ship will _______ in the new rules.
2. “That didn’t _______ me,” the alien said, even though she was shaking.
3. It’s time to _______ in the new telescope upgrades.
4. Do you remember that _______ you went through when you’d only eat space hot dogs?
5. In five seconds, when he shouts “Evacuate!” he will _______ the crew.

Answers: 1. phase (verb) 2. faze 3. phase (verb) 4. phase (noun) 5. faze

An aside for Star Trek fans
I’ve been wondering why the Star Trek weapons are called phasers and not fazers. It seems to me that since they have the ability to stun (faze) people, they should be called fazers. But maybe it has something to do with cycles (phases) of energy the weapon produces—thus phasers.

If you happen to have ideas about this conundrum, would you please let me know? It’s, like, really important.