I was reading an article written by a Native Speaker when I came across a statement like: The word can be difficult to clearly define and hence count. I do know that this had been paraphrased from another researcher's work. I, however, am having a difficult time justifying the active use of the verbs define and count. I surmise they have to be replaced by passive-voice ones.
It sounds fine to me as a native speaker. Each verb is in the infinitive form. (Some pedants will say that an infinitive shouldn't be "split," meaning that you shouldn't put words between "to" and the verb form. Maybe that's what's confusing you here. Maybe this will clarify it:
The word can be difficult to clearly define and hence count.
The word can be difficult to define and count.
The word can be difficult to define and to count.
This is what the sentence means at its core. (Although I'm not sure what it means to "count" a word. Maybe that's clearer from the context.)