5.4: Modals of Obligation or Necessity
- Page ID
- 371574
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\(\newcommand{\avec}{\mathbf a}\) \(\newcommand{\bvec}{\mathbf b}\) \(\newcommand{\cvec}{\mathbf c}\) \(\newcommand{\dvec}{\mathbf d}\) \(\newcommand{\dtil}{\widetilde{\mathbf d}}\) \(\newcommand{\evec}{\mathbf e}\) \(\newcommand{\fvec}{\mathbf f}\) \(\newcommand{\nvec}{\mathbf n}\) \(\newcommand{\pvec}{\mathbf p}\) \(\newcommand{\qvec}{\mathbf q}\) \(\newcommand{\svec}{\mathbf s}\) \(\newcommand{\tvec}{\mathbf t}\) \(\newcommand{\uvec}{\mathbf u}\) \(\newcommand{\vvec}{\mathbf v}\) \(\newcommand{\wvec}{\mathbf w}\) \(\newcommand{\xvec}{\mathbf x}\) \(\newcommand{\yvec}{\mathbf y}\) \(\newcommand{\zvec}{\mathbf z}\) \(\newcommand{\rvec}{\mathbf r}\) \(\newcommand{\mvec}{\mathbf m}\) \(\newcommand{\zerovec}{\mathbf 0}\) \(\newcommand{\onevec}{\mathbf 1}\) \(\newcommand{\real}{\mathbb R}\) \(\newcommand{\twovec}[2]{\left[\begin{array}{r}#1 \\ #2 \end{array}\right]}\) \(\newcommand{\ctwovec}[2]{\left[\begin{array}{c}#1 \\ #2 \end{array}\right]}\) \(\newcommand{\threevec}[3]{\left[\begin{array}{r}#1 \\ #2 \\ #3 \end{array}\right]}\) \(\newcommand{\cthreevec}[3]{\left[\begin{array}{c}#1 \\ #2 \\ #3 \end{array}\right]}\) \(\newcommand{\fourvec}[4]{\left[\begin{array}{r}#1 \\ #2 \\ #3 \\ #4 \end{array}\right]}\) \(\newcommand{\cfourvec}[4]{\left[\begin{array}{c}#1 \\ #2 \\ #3 \\ #4 \end{array}\right]}\) \(\newcommand{\fivevec}[5]{\left[\begin{array}{r}#1 \\ #2 \\ #3 \\ #4 \\ #5 \\ \end{array}\right]}\) \(\newcommand{\cfivevec}[5]{\left[\begin{array}{c}#1 \\ #2 \\ #3 \\ #4 \\ #5 \\ \end{array}\right]}\) \(\newcommand{\mattwo}[4]{\left[\begin{array}{rr}#1 \amp #2 \\ #3 \amp #4 \\ \end{array}\right]}\) \(\newcommand{\laspan}[1]{\text{Span}\{#1\}}\) \(\newcommand{\bcal}{\cal B}\) \(\newcommand{\ccal}{\cal C}\) \(\newcommand{\scal}{\cal S}\) \(\newcommand{\wcal}{\cal W}\) \(\newcommand{\ecal}{\cal E}\) \(\newcommand{\coords}[2]{\left\{#1\right\}_{#2}}\) \(\newcommand{\gray}[1]{\color{gray}{#1}}\) \(\newcommand{\lgray}[1]{\color{lightgray}{#1}}\) \(\newcommand{\rank}{\operatorname{rank}}\) \(\newcommand{\row}{\text{Row}}\) \(\newcommand{\col}{\text{Col}}\) \(\renewcommand{\row}{\text{Row}}\) \(\newcommand{\nul}{\text{Nul}}\) \(\newcommand{\var}{\text{Var}}\) \(\newcommand{\corr}{\text{corr}}\) \(\newcommand{\len}[1]{\left|#1\right|}\) \(\newcommand{\bbar}{\overline{\bvec}}\) \(\newcommand{\bhat}{\widehat{\bvec}}\) \(\newcommand{\bperp}{\bvec^\perp}\) \(\newcommand{\xhat}{\widehat{\xvec}}\) \(\newcommand{\vhat}{\widehat{\vvec}}\) \(\newcommand{\uhat}{\widehat{\uvec}}\) \(\newcommand{\what}{\widehat{\wvec}}\) \(\newcommand{\Sighat}{\widehat{\Sigma}}\) \(\newcommand{\lt}{<}\) \(\newcommand{\gt}{>}\) \(\newcommand{\amp}{&}\) \(\definecolor{fillinmathshade}{gray}{0.9}\)Hidden Hikes in Orange County
| Modal | Form Type | Usage & Examples | Special Rules & Notes |
|---|---|---|---|
| MUST | Positive | Strong obligation/necessity
Hikers must carry water on the Santiago Oaks trail.
You must register before entering Crystal Cove backcountry.
|
Cannot be used for past tense
Very formal/strong
|
| Negative (must not) |
Strong prohibition
Visitors must not leave the designated trails at Laguna Coast.
You must not disturb wildlife in Whiting Ranch.
|
PROHIBITION - completely forbidden
|
|
| Question | Asking about strong necessity
Must we bring permits for camping at El Moro?
|
Very formal, rarely used in speech
|
|
| Past | Not possible with MUST
❌ We musted bring flashlights.
|
Use "had to" for past necessity
|
|
| HAVE TO | Positive | Necessity/obligation (less formal)
We have to check weather conditions before hiking Saddleback.
She has to wear proper shoes for the Trabuco Canyon trail.
|
NO CONTRACTION: We've to ❌
More common in everyday speech
|
| Negative (don't have to) |
No necessity/optional
You don't have to bring a guide for Peters Canyon.
We don't have to start early for this easy Irvine Park trail.
|
Means "not necessary" NOT "prohibited"
|
|
| Question | Asking about necessity
Do we have to make reservations for Caspers Wilderness Park?
|
Common in everyday speech
|
|
| Past (had to) |
Past necessity
Yesterday we had to turn back because of fog at Modjeska Peak.
|
Only way to express past necessity
|
|
| HAVE GOT TO | Positive | Strong necessity (informal)
We've got to leave early for the Backbone Trail hike.
You've got to see the hidden waterfall in Holy Jim Canyon.
|
CAN contract: We've got to ✓
Very informal, like "must" but casual
|
| Negative (haven't got to) |
No necessity (rare usage)
We haven't got to rush on this gentle Aliso Creek trail.
|
Rarely used - prefer "don't have to"
|
|
| Question | Asking about necessity (informal)
Have we got to bring our own water to Limestone Canyon?
|
More common in British English
|
|
| Past | Not commonly used in past
Use "had to" instead
|
Use "had to" for past necessity
|
Key Contraction Rules:
- HAVE TO: Cannot contract with subject (We've to ❌)
- HAVE GOT TO: CAN contract with subject (We've got to ✓)
- MUST: No contractions possible