“hone,” “less,” and “can,” when they mean “home,” “fewer,” and “may.”

“Hone” means to sharpen, so it’s natural for us to use it when we mean to sharpen our focus or move closer to a precise point. But that would be incorrect. As we narrow our search, we “home” in.

Scientists have honed homed in on how statins affect the risk of individual malignancies.

Tip: Used correctly, “hone” will never be followed by the preposition “in.”

“Less” refers to the measurement of something that cannot be separated, like shade. “Fewer” refers to discrete items, like trees. I don’t know how much Ford pays its ad agency, but the following appeared across the middle of a full-page advertisement for the new Ford Escape Hybrid:

That means less fewer trips to the gas station.

Tip: If you can count the items, use “fewer.”

A friend from the Midwest remembers frequently asking his mother, “C’n I go out and play?” And his mother just as frequently responding, “You can and you may.” You are able and you have my permission. Legislators should listen to Mom; they often construct rules and regulations to say a citizen does not have the ability to violate them, when they mean the citizen does not have permission to violate them.

Disciplinary rules are mandatory and state the minimum level of conduct below which no practitioner can may fall without being disciplined.

Even major newspapers get this wrong:

A public law school in California can may deny recognition to a Christian student group that refused to accept gay members, the Supreme Court ruled.

Tip: This usage problem is so prevalent, and so easy to overlook, I would do a word search to check every “can.”