As a professor, I see a lot of student writing, some good, some not so good. And I’m one of those people who think that a professor’s job includes teaching writing, regardless of the discipline one belongs to. So here is my first foray into advice on writing.

In the last couple of years, I have noticed that many students use “similar” incorrectly. I often see sentences structured like the following:

Similar to protein A, protein B binds to protein C.

So what’s the problem? To understand that, we have to ask what “Similar to protein A” modifies. What the writer is trying to say is that protein B behaves like protein A in that both bind to protein C. It’s the entire action of protein B modifying protein C that is similar to the action of protein A. Therefore, “Similar to protein A” is modifying the entire principal clause. However, “similar” is an adjective, so it should modify a noun. “Similar” therefore can’t be right.

A modifier of a clause can only be an adverb, so a correct version of the above sentence would be

Similarly to protein A, protein B binds to protein C.

“Similarly” (note the -ly ending) is an adverb, so it can modify an entire clause. Problem solved.

Of course, this isn’t the only solution. It’s always good to have more than one way to say something so you can vary the style of your text a little bit. Sometimes, the simplest way to say something is the best, so one alternative is to replace the adverb by a common preposition:

Like protein A, protein B binds to protein C.

The truth is, though, that neither of the above sentences probably says what the student who wrote it wanted to say. All these sentences really say in the end is that both A and B bind C. However, these constructions often show up in text where a student is actually trying to say that the two proteins bind C in a similar way (using similar contact surfaces, etc.). Why not just say that?

Protein B also binds protein C. B and C make similar contacts as A and C in the respective complexes.

Note that I turned one sentence into two. My meaning is now completely clear and unambiguous. This is another lesson: unless you’re strictly space limited for some reason, sometimes it’s better to use a couple of sentences and a few extra words in order to make your meaning completely clear. Similarity, for example, is a slippery complex. Saying that two things are similar really doesn’t tell us much unless we say in which ways they are similar. Similar comments apply to many other constructions. When writing, ask yourself what you want to say, and then make sure that the words you use convey your meaning without ambiguity.