Introduction

Being bound by duty or responsibility or subject to external constraints is as ancient as humanity itself.

Whole systems of laws have been developed to codify such relations and the language of everyday life reflects this but also determines it.

Despite its supposed crispness and precision, however, legal language often lags behind the vernacular language of custom in conveying subtler distinctions.

Some modal and semi-modal verbs are used to describe such constraints, duties and responsibilities.

Part 1: ‘have to’ and ‘need (to)’

Perhaps the most basic of constraints are those placed upon us by nature.

For these natural laws we often use the so-called Present Simple

[1] Heavy objects fall to earth.

When these natural constraints apply to us, we use ‘have to.’ So, just as we have lungs to breathe and stomachs to digest our food, we have to breathe and we have to eat.

‘Have to’ usually refers to the constraint in general.

If you are feeling the effects of such a physical constraint, you can use ‘need to’.

[2] I’m hungry. I need to eat something.’

[3] Open a window. I need to breathe.

Speakers sometimes switch from ‘need to’ to ‘have to’ to increase the degree of urgency.

[4a] I need to pee (some time soon)

[4b] I have to pee (right now)

[5a] I need to leave at 4 pm sharp.

[5b] I’m sorry. I have to leave now. Something has come up.

By extension from the constraints imposed by the natural world, in everyday language, legal regulations and personal responsibilities can also be referred to using ‘have to’ and ‘need to’.

[6] You have to apply for a passport if you want to go abroad

[7] You have to be over 18 to drive

[8] She has to be at work by 9 am

In all of the examples above, you can also use ‘need to’ without substantially altering the meaning. ‘Need to’ however reduces the degree of external coercion somewhat, shifting the focus to the subject’s predicament. It could be used, for example, to soften a bureaucratic requirement or make a medical procedure seem less daunting.

[9] You need to fill in this form (polite bureaucrat)

[10] You need to swallow this pill (kindly health professional)

When applied to inanimate objects a different form—‘need  + -ing’—is used.

[11] The lawn needs mowing.

[12] My hair needs cutting.

but

[13] I need to get my hair cut.

We tend to efface the person who actually does the cutting or mowing. We also avoid using ‘need to’ when the doer is explicitly mentioned. We would not normally say for example, ‘The hairdresser needs to cut my hair’. Nor ‘The hairdresser has to cut my hair,’ unless we are a little princess and have the power to order the hairdresser to do so.

We might, however, use ‘have to’ in situations where we are referring to some kind of regulation or social norm to which we are expected to conform.

[14] Residents of suburban neighborhoods feel that they have to mow their lawns regularly

Here there is no question of ‘needing’ because the neighbors do not have a desire or intention that comes from within.

Consider also the following examples, where various shades of meaning are orchestrated using various formulations using ‘have to’ and ‘need’:

[15] My mum says I have to get my hair cut (sense of slight irritation or reluctance—obligation external)

[16] My mum says I need to get my hair cut (more neutral and accepting)

[17] My mum says my hair needs cutting (likewise neutral)

[18] My mum says my hair has to be cut (very strong—the youngster’s hair will be cut by some external agent with the subject having no say in the matter—an army barber for example)

[19] ‘My mum says my hair needs to be cut’ – (again there is some external agency involved – the subject needs to get their hair cut before starting a new job, for example)

Language is subtle indeed.