home in
Home in, like a homing pigeon. Hone means to sharpen.
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Wrong: Let’s hone in on the root cause.
Right: Let’s home in on the root cause.
Homing in is navigation, like a missile or a pigeon.
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Wrong: Time to home your skills.
Right: Time to hone your skills.
Sharpening. That’s hone, and it takes no in.
The two words
Home in comes from homing pigeons and later homing missiles—moving progressively closer to a target. It always takes in or in on.
Hone means to sharpen on a whetstone. You hone a blade, or a skill. It doesn’t take in, because sharpening isn’t directional.
The honest caveat
Hone in is common enough that several dictionaries now record it as a variant, and it’s been drifting that way since the 1960s. It’s still the one people notice, and home in is never wrong.
Now go home in on it.