- There were huge machines at his plant.
- There were large machines at his plant.
Which one sounds better? Are they both grammatical? Could you please explain any differences between the two as they are both very confusing for me.
Of course, both sentences are grammatical. "Huge" and "large" are in the same category: they are adjectives. However, something huge is surprisingly large or excessively large. If something is large, but about as large as can be expected, then it is not huge.
Huge is an emphatic word, and has subjective connotations: what one person might call big --- or even small! --- someone else might call huge. A teenage girl about to go to a dance might think she has a "huge" zit (acne spot) on her chin, but to someone else it might appear small and insignificant.
For instance, have you ever heard of someone ordering a "huge coffee" in a coffee shop? If there were such a thing on the menu, it would be understood as humor. Even ridiculous drink sizes like 64 oz drinks are not called "huge", but "super sized" or whatever.
Or how about clothing: a T-shirt can be "large", and then "extra large". "Huge" is not used because it's an emotional word; it does not work well with cold facts like objectively established sizes, and could even be offensive to someone because of its possible connotations of "excess".
Yes, they are both grammatical. They are synonymous for the most part, although huge will sometimes evoke a mental image that is larger than large.
Here's one way you could look at it: A horse is a large animal; an elephant is a huge animal.
That said, adjectives describing size are relative, and context-dependent. How big is huge? That depends. A large tumor might be just 4 or 5 cm across, and a huge tumor might be 12 or 13 cm across.
As far as machinery goes, large machines are too heavy to lift. Huge machines are too heavy to even think about lifting.
As far as grammaticality goes, it might be worth pointing out that superlatives larger and largest are relatively common words, but, for some reason, huger and hugest aren't used very often, and they even sound a little bit "off" to me.
When I Googled "huge machines," I got images like this one. Note the large yellow tractor in the picture:
Insofar as machinery goes, I would probably call this a large factory robot: