AKA: phrasal modals

Examples

Before the mid-19th century, most people weren’t able to read.

I'm supposed to mark you absent if you are 10 minutes late.

You have to be more careful.

We’re going to write a letter to the editor.

🧾Definition

Phrasal modals carry similar interpersonal meanings to “pure” modal verbs (can, could, may, will, should, must, etc.) but with important differences in function and use. Like all modal verbs, they express a stance towards the main verb. However, the authority or obligation is usually more external than internal with a phrasal modal verb. The phrasal modals can be lined up with their related pure modal:

🔬Discovery

✅Form

The big structural difference between pure modals and phrasal modals is that phrasal modals start with a regular verb that needs to be inflected (be or have). This means they can take different tenses (I am able, I was able, I will be able to …). Used to is an exception that’s discussed under past habitual. Also, all the phrasal modals end with to, so they appear to be followed by the to infinitive, not the bare infinitive.

<aside> ⚠️ Careful!

• Some learners will try to add to to pure modals by analogy to phrasal modals (*I must to go).
• It is easy for MLLs to forget the be or have verb (I going to, she supposed to). This is not usually a problem in speaking, but it is an error in formal written registers.
• Phrasal modals can be heavily reduced in fluent speech. For example, We have got to go naturally becomes we gotta go; I’m going to look becomes I’m gonna look (or in some varieties, I’mma look). These reductions are neither slang nor incorrect, and some of them occur even in quite formal speaking situations like lectures or political speeches. However, they should be avoided in writing unless the writer is trying to reflect the nuances of spoken English, for instance in dialogue.
• WEIRD! The negative forms of must and have to behave strangely:
  • You must/have to register online. (It’s a requirement).
  • You must not register online. (It’s not allowed)
  • You don’t have to register online. (It’s not required) </aside>

💬Functions

Many grammar textbooks go to great lengths to differentiate phrasal and pure modals in terms of their meaning and use. The reality is much messier. However, here are some differences in function and meaning which are useful:

• Can/could are more frequent than be able to. Be able to is most useful for emphasizing past time, which isn’t always clear with could (e.g.,
  • I wasn’t able to find you yesterday (ability)
  • I couldn’t find you yesterday (ability or possibility?)
• Will  and be going have somewhat different functions, although it’s hard to imagine a context where a speaker would miscommunicate by choosing the wrong form:
  • will: sudden decisions, promises, schedules
  • be going to: future plan, actions that can be predicted from the present, weather
• Should, must, and may are pure modals, so they suggest that the speaker is expressing an internal motivation. Supposed to, allowed to, and have to can suggest that the authority is external. This distinction is quite subtle and even debatable, but compare:
  • I should exercise more (I know I need to do this)
  • I’m supposed to exercise more (my doctor tells me, but I’m not convinced)
  • I must make an appointment (because I want to).
  • I have to make an appointment (or there will be trouble).
  • You can/may turn your paper in late (because I’m giving you permission).
  • You’re allowed to turn your paper in late (because that’s the syllabus policy).

📝Practice