When you look up the meaning of a verb (action word) in the dictionary you may have trouble finding it.  This is because most dictionaries list verbs as infinitives.  That is, you will find the word incubate easily in a dictionary, but you may not find incubates, incubated or incubating. The infinitive is the basic form of the verb, and in English it usually has the word to in front of it (eg to ask, to see,etc).  The infinitive doesn't give any idea of which person is involved, or how many people or things, or any notion of time (past present or future).  In French infinitives don't have a word in front of them - avoir (to have), etre (to be), etc.  You remember your French verbs in this form.

Some people think that (in English) it is a great crime to put a word or words between 'to' and the verb, eg 'to completely understand.'  This is called 'splitting the infinitive.'  Probably the most famous example of this is from the start of each episode of Star Trek: 'to boldy go where no man has gone before.' 

One or two famous writers have taken exception to having their split infinitives corrected.  The brilliant crime writer Raymond Chandler (get one of his books and read it), once wrote to his publisher:

"When I split an infinitive, God damn it, I split so it will stay split."