"I have a few pants bought from Mark and Spencer that need to be altered." [closed]

"I have a few trousers bought from Mark and Spencer that need to be altered." In this context "need" or "needs to be altered"?

TLDR: That should instead read:

• I have a few pairs of trousers that need to be altered.

On pluralia tantum

Like the words cattle, scissors, and genitals, the words pants and trousers are what specialists in these matters refer to as pluralia tantum. That means that they are defective¹ nouns that only show up already plural in form with no corresponding singular noun to go with their plural versions.²

It also means for lack of a singular, they can never be used as count nouns, since that would require the existence of a singular — which is what you have ungrammatically attempted to do here. Because there is no such thing as ⁕one trouser or ⁕a trouser, neither is there such a thing as ⁕a few trousers, either, which is why your formulation is ungrammatical.

You therefore must only use such pluralia tantum “partitively” — as though they were mass nouns — such as by saying this pair of trousers, or these pairs of trousers, or a few pairs of trousers. That way the word for the set, here pair/pairs, carries the actual number governing agreement with the verb.

• This pair of trousers needs to be altered. [singular subject and verb]
• These pairs of pants need to be altered. [plural subject and verb]
• I have a few pairs of pants that need to be altered. [plural subject and verb]

You can search for other postings on this site related to these grammatical oddities via this link.

On semi-modal verbs used as modals

Three may also be some confusion here over your choice of need/needs that stems from that verb’s occasional use as a true modal, a word-class that is also defective with respect to inflectional variants. The semi-modal verb need, which is used as a true modal only in negative or formal interrogative contexts, does not inflect for person, number, or tense when a modal. It also takes only a bare infinitive not a to-infinitive when doing so:

1. This pair of pants needs to be altered. [singular subject and verb]
2. This pair of pants does not need to be altered. [singular subject and verb]
3. This pair of pants need not be altered. [singular subject but modal verb]

The inverted negative in need not is what triggers true modal use there in the final example.

Another semi-modal verb that can be used in this curious way is dare and for some speakers, ought. Like need, these can be true modals only in negative or interrogative contexts. They might sound formal to some writers, or not occur at all in some speakers.

Footnotes

1. A “defective” word in some word-class is one that does not admit some or all of the inflectional variants which that particular word-class is subject to under regular inflectional morphology. So for example, a defective noun might be one without any plural to go with it, a defective verb might be one with only a past tense but no present tense, and a defective adjective might be one that has no comparative degree formed by adding -er.

2. Attributive use like pant leg, genital mutilation, or scissor kick doesn’t count as an actual singular, because even a plurale tantum like these take a form that doesn’t look plural when it is used attributively to modify another noun. But compare cattle prod because there is no way to “make” the word cattle look singular (unlike with pants, scissors, and genitals, three words that you hope never to find together in the same sentence).