Secondary verb types
None of the Secondary-A verbs have any independent semantic roles. Basically, they modify the meaning of a following verb, sharing its roles and syntactic relations.
Many tens of thousands of words have been written about the English modals. Only some of the main points of their grammatical and semantic behaviour are indicated here.
There are two, syntactically different but semantically related, types, MODALS and what we can call SEMI-MODALS:
|be going to||prediction|
have got to
|can/could||be able to||ability|
|--||be about to||imminent activity|
|be to||--||scheduled activity|
|--||be bound to||inevitability|
We mentioned at the end of §3.4 that a clause may contain a chain of verbs, each in syntactic relation with its neighbours, e.g. She will soon be able to begin telling John to think about starting to build the house. A modal must occur initially in such a chain--that